Part 26

PATHOLOGY AND PATHOGENESIS.--Notwithstanding that this disease has been recognized for two centuries and a half, that abundant opportunity has been furnished for its post-mortem investigation, and that experimental physiology has contributed much information bearing upon the subject, its pathology is still undetermined. Experiment has, however, rendered it very likely that all cases of essential glycosuria--that is, all cases in which saccharine urine is not the direct result of over-ingestion of sugar or sugar-producing food--are accompanied by a hyperæmia of the liver. This hyperæmia, with its consequent glycosuria, can be induced by puncturing or irritating the so-called diabetic area in the medulla oblongata. This area corresponds with the vaso-motor centre, and with the roots of the pneumogastric or vagus nerve in the floor of the fourth ventricle; whence it was at first inferred that this nerve is the excitor nerve of glycosuria. It was soon ascertained, however, that when the pneumogastric was cut, glycosuria ensued only when the central end was stimulated, while {196} stimulation of the peripheral portion was without effect. Whence it became evident that this nerve is not the excitor, but the sensory nerve concerned in glycogenesis.

It was also learned in the course of continued experiment that glycosuria resulted upon transverse section of the medulla oblongata, of the spinal cord above the second dorsal vertebra, of the filaments of the sympathetic accompanying the vertebral artery, upon destruction or extirpation of the superior cervical ganglion, and sometimes, but not always, after division of the sympathetic in the chest (Pavy); also after section or careful extirpation of the last cervical ganglion, section of the two nerve-filaments passing from the lower cervical to the upper thoracic ganglion around the subclavian artery, forming thus the annulus of Vieussens, and after section or removal of the upper thoracic ganglion.

Trach., trachea; Ca., carotid artery; n. vag., the vagus trunk; n. rec., the recurrent laryngeal; sym., the cervical sympathetic nerve ending in the inferior cervical ganglia, gl. cerv. inf. Two roots of the ganglion are shown--rad., the lower of the two accompanying the vertebral artery, A. vert., and being the one generally possessing accelerator properties; gl. thor. pr., the first thoracic ganglion. Its two branches, communicating with the cervical ganglion, surround the subclavian artery, forming the annulus of Vieussens. sym. thor., the thoracic sympathetic chain; n. dep., depressor nerve. This is joined in its course by a branch from the lower cervical ganglion, there being a small ganglion at their junction, from which proceed nerves to form a plexus over the arch of the aorta. It is this branch from the lower cervical ganglion which possesses accelerator properties, hence the course of the accelerator fibre is indicated in the figure by the arrows. (Modified from Foster's Physiology.)]

All these operations paralyze the vaso-motor nerves by which, in health, the blood-vessels of the liver are kept in a state of tonic contraction; hence these vessels dilate when the nerves are cut. From the facts named we also learn the path of the glycogenic influence, which must be from the medulla oblongata into the spinal cord, thence by the filaments of the {197} sympathetic which accompany the vertebral artery into the lower cervical ganglion; thence through the annulus of Vieussens into the first dorsal ganglion; and thence through the prevertebral cord of the sympathetic, and branches not precisely determined, to the hepatic blood-vessels as shown by the dotted line in Fig. 3.

I say, by branches of the sympathetic not precisely determined, because our power to produce artificial diabetes fails below the first thoracic ganglion; for section of the sympathetic between the tenth and twelfth ribs, and of the splanchnics, is not followed by glycosuria, although the vaso-motor nerves to the liver are known to pass through them.

According to Eckhard, the phenomena of artificial glycosuria are irritative and not paralytic. This view he believes sustained by his own experiments, according to which if the splanchnics, through which {198} the vaso-motor nerves of the liver pass, are cut prior to the diabetic puncture, not only does this operation fail to produce glycosuria, but it even renders ineffectual the puncture itself as well as the section higher up. But Cyon and Aladoff remind us that it is not mere dilatation of the hepatic vessels, but increased velocity in the movement of the blood, which deranges the sugar-assimilating function and causes glucose to appear in the urine. The vaso-motor nerves of the intestinal blood-vessels also pass through the lower part of the sympathetic and the splanchnics, and section of the latter must cause these blood-vessels to dilate. Now, in rabbits, in which this experiment is usually performed, the digestive canal is very long, and the blood-vessels so capacious that when dilated they hold as much blood as all the rest of the vascular system together, so that when the lower sympathetic and splanchnics are cut, so much blood goes into the intestines that the increased velocity required in the blood-vessels of the liver to produce glycosuria is impossible. But if the vessels of the liver be first dilated by puncturing the floor of the fourth ventricle, section of the sympathetic or of the splanchnics may then be made without arresting the formation of sugar; whence it would appear that the glycogenic influence may still pass through the lower sympathetic and splanchnics.

In view of the fact that Eckhard has failed to confirm the results of Cyon and Aladoff, but has traced the glycogenic influence down the spinal cord as far as the fourth dorsal vertebra in rabbits, and even a little lower, and that Schiff has shown that diabetes sometimes results after section of the anterior columns of the cord between the medulla and the fourth cervical vertebra, Dr. Brunton suggests that the vaso-motor nerves of the liver may not always leave the spinal cord to join the sympathetic by the branches accompanying the vertebral artery, but sometimes pass farther down the cord, leaving it by the communicating branches to some of the dorsal ganglia, as indicated in Fig. 4.

It is evident that an agency involving any part of this tract in such a way as to paralyze the vaso-motor nerves of the liver is capable of producing glycosuria. Such cause may operate upon the central ganglia whence the nerves emanate, as the vicinity of the oblongata and upper parts of the spinal cord or the coeliac ganglion and its branches, including those to the pancreas. Or the irritation may be peripheral and its effects reflex. We have seen that irritation of the central end of the cut vagus will produce glycosuria. Any irritation, therefore, involving the peripheral distribution of this nerve may produce it. Hence embarrassed respiration, whether due to disease of the respiratory passages, strangulation, or inhalation of irrespirable gases and anæsthetics, produces glycosuria in dogs and rabbits; and this symptom has been known to attend these conditions in the human subject. So, too, glycosuria may be produced by such substances as woorara, strychnia, morphia, and phosphoric acid, introduced into the blood and irritating the terminal filaments of the pneumogastrics, or it may be brought about secondarily through the embarrassed respiration these drugs produce. Such peripheral {199} irritation may reside also in the stomach, intestines, liver, or any organ to which the pneumogastric is distributed.

It is not unlikely that irritation of the extremities of sensory nerves other than the pneumogastric may become the cause of reflex glycosuria. Even puncture of the floor of the fourth ventricle itself may be reflex in its operation, the roots of the pneumogastric being thus irritated. The effect of the irritation conveyed to the glycogenic centre is to inhibit the usual tonic influence of the vaso-motor nerve upon the vessel walls. Among the experimental irritations, in addition to puncture of the floor of the fourth ventricle, which produce glycosuria by reflex action, are injuries of the cerebral lobes and cerebellum, optic thalami, cerebral peduncles, pons varolii, middle cerebellar peduncles, and even of the sciatic nerve and brachial plexus; whence it may be inferred that pathological irritation in the same situations may result in a glycosuria, which is temporary or permanent according as the irritation is temporary or permanent.

Finally, there is no reason why an inhibitory reflex action should not originate in the sympathetic itself. When we remember that this nerve is both sensory and motor in function, and that the inhibitory influence to which the heart's action is subject is accomplished through the sympathetic as a sensory nerve and the pneumogastric as a motor, there is no reason why similar results may not be brought about by the sympathetic alone. This being the case, we need not ascribe glycogenic phenomena to irritation in Eckhard's sense--that is, to a direct stimulant action of the irritant upon the vaso-motor nerves of the liver--but may suppose a sensory influence to ascend one set of sympathetic filaments and an inhibitory influence to descend through another.

Dr. Pavy has recently put forward some chemical theories which explain the action of the hyperæmia in producing glycosuria, but they do not account for the hyperæmia itself. In healthy digestion the carbohydrates (starch and sugar) are converted, not into glucose, but into maltose, C{12}H{22}O_{11}, dextrin being intermediate in composition. Maltose is absorbed and assimilated, converted into glycogen. So, too, when glucose is ingested as such, it is converted by the glucose ferment into maltose in the stomach and intestines. For the proper production of maltose and its assimilation a good venous blood, producing a maltose-forming ferment, is necessary. In diabetes, in consequence of the dilatation of the arteries of the chylopoëtic viscera, the blood enters the liver too little deoxygenated, and a glucose-forming ferment is produced. The glucose thus formed is not assimilable, but passes off into the circulation and the urine.

MORBID ANATOMY.--Such are some of the facts bearing upon the pathology of diabetes mellitus. Throwing out the milder type of cases, in which glycosuria is the result of an over-ingestion of saccharine and sugar-producing food--and these can scarcely be called instances of essential diabetes--it is evident that glycosuria may be produced in a variety of ways operating through the nervous system; and accordingly we may infer that there is scarcely an organ in close relation with the sympathetic system derangement of which is not capable of producing it. Among these we would naturally expect to find conspicuous alterations in the nervous centres, and yet I have never found changes in these centres after death. At the same time, others have noted meningitis, tubercular {200} and traumatic, apoplectic effusions, and tumors of the brain, especially in the neighborhood of the medulla oblongata. The alterations in the nerve-centres described by Dickinson as the essential morbid anatomy of diabetes I have looked for in vain. These changes are described as a cribriform or porous condition of the white nervous matter, said to be visible to the naked eye. The spaces thus produced are partially occupied by dilated blood-vessels, which, in turn, are surrounded by dilated perivascular sheaths and broken-down nervous matter, into which extravasations of blood have taken place, as evidenced by the presence of pigment-granules. The changes are found in the white matter of the convolutions of the brain, but fewer and larger in the central portions. The corpora striata, optic thalami, pons, medulla, and cerebellum are favorite seats for the largest and most striking holes. In rapidly-fatal cases the cavities are sometimes filled with a translucent, gelatinous substance, containing, besides vascular elements, the globular products of nervous disintegration. In the more chronic forms of the disease, as it occurs in elderly persons, the excavations are usually empty, although the elements of nervous decay are still to be found fringing the margins or collected as an irregular sheath upon the dilated or shrunken artery. There are changes in the cord similar to those in the brain, but less decided. But the most striking alteration in the cord, according to Dickinson, although not always present, is dilatation of the central canal, which in the dorsal and lumbar regions is sometimes expanded to many times its normal diameter, and forms a conspicuous object immediately after the cord is divided.

These alterations have eluded the vigilance of other pathologists who have sought for them in well-determined cases of diabetes mellitus, while they have been found, on the other hand, in the nervous centres when no diabetes was present. In the recent discussion on diabetes at the Pathological Society of London, Douglas Powell seemed to be the only one who was convinced that most of Dickinson's specimens were examples of positive lesions.

A hyaloid thickening of the blood-vessels of the brain has been noted by Stephen Mackenzie and Seymour Taylor in some cases, and miliary aneurisms of the retina in one.

Of other organs, one of the most frequently found diseased is the pancreas, and, according to Senator, it is fair to assume that disease of the pancreas is present in about one-half of all cases of diabetes. As the result of increased experience, I am inclined to attach much more importance to pancreatic disease as a cause of diabetes than I did a few years ago. Among the changes found is a pseudo-hypertrophy, which consists chiefly in a hyperplasia of the connective tissue, fatty degeneration of the gland-cells, and atrophy of the glandular structure; cancerous disease; calculous concretions in the ducts with or without obstruction; and cystic dilatation.

Facts bearing upon the relation of pancreatic disease to diabetes have been accumulating since Cowley first discovered calculi in the pancreas of a diabetic, and Bright pancreatic cancer in a similar case. Since then {201} instances have multiplied to such extent that it would be unprofitable to enumerate them. But in 1877, Lancereaux communicated to the French Academy of Medicine specimens of profound lesion of the pancreas from cases dying of diabetes mellitus. This, he alleged, constitutes a special and distinctive variety of diabetes, characterized by sudden onset, emaciation, polydipsia, polyphagia, and peculiar alvine dejections. More recently, Depierre has confirmed these observations, apparently establishing this variety of diabetes mellitus, of which a very rapid course--six months to three years--and the habitual presence of diarrhoea are characteristic; while the presence of greasy or creamy stools, and the appearance in them of undigested nitrogenous substances, may aid in the diagnosis. Precisely such a case, running the same rapid course--less than one year--with emaciation, uncontrollable diarrhoea, creamy stools, jaundice, and pancreatic disease, came under the writer's care in 1882. At the autopsy the pancreas was found enlarged, and numerous gritty particles were disseminated through it.

Supposing such pancreatic disease to be primary, it is evident that it must operate through the coeliac plexus, which, with its ganglion, is gradually encroached upon. On the other hand, it is also possible that the disease of the coeliac plexus may be primary, and the coexisting pancreatic disease and diabetes mellitus both secondarily dependent upon it. This can only be settled by more careful study of the coeliac plexus after death from diabetes, but up to the present time facts would seem to support the view of primary pancreatic disease.

The liver is frequently enlarged--sometimes but slightly, at others decidedly. It has been known to reach three times the size of the normal organ. Again, it may be darker and harder--hyperæmic. By minute examination the acini are found enlarged, the capillaries dilated and distended; the liver-cells are enlarged, distinctly nucleated, rounded, and indistinct as to their outline, appearing to fuse into each other. A weak solution of iodine strikes a wine-red color, which, according to Rindfleisch, is confined to the nucleus, but, according to Senator, may extend to the whole cell. This reaction Klebs ascribes to post-mortem changes in the glycogenic substance. They are more striking in the portal or peripheral zone of the lobule, while the intermediate or hepatic artery zone is often fatty, and the central part, surrounded by the rootlets of the hepatic vein, is nearly normal. Stockvis and Frerichs ascribe the enlargement of the liver partially to a new formation of liver-cells--in other words, to a true hypertrophy. At other times the organ has been found reduced in size.

Dickinson, Trousseau, and Budd describe an overgrowth of connective tissue, as well as of the cells of the liver, producing a hypertrophic cirrhosis.

According to Beale, Frerichs, and Folwarczny, the fat which is found in small proportion in the liver-cells in health is often diminished, and even absent, and quantitative analysis by the last-named observer {202} confirms this view. Such diminution may be the forerunner of an atrophy of liver-cells which has been noted, and which, as the disease continues, leads to the atrophy referred to as occasionally present. On the other hand, intense fatty degeneration of the entire organ, similar to that found in phosphorus-poisoning, has been met by Gamgee, associated with a lipæmic state of the blood and symptoms of acute acetonæmia.

The kidneys, in cases which have continued some time, are apt to be hyperæmic and enlarged, although primarily they are uninvolved. It would seem that the long-continued hyperæmia which is a necessary condition of the copious secretion of urine, results, sooner or later, in an over-nutrition of the renal epithelium, a widening of the tubules, and consequent enlargement of the whole organ. The changes are mainly of a parenchymatous or catarrhal rather than an interstitial nature, the epithelium being disposed to shed. These changes may reach a more advanced stage of cellular degeneration, and may be attended by albuminuria. The cells may become very large, present a yellowish-brown color, their nuclei indistinct and non-responsive to ordinary staining solutions, but may take a red stain with a weak solution of iodine, similar to that described in the case of the liver-cells. Mackenzie describes a hyaline degeneration of the intima of the arterioles and a skeleton condition of the epithelium of the collecting tubes. There may also be a catarrh of the pelves of the kidneys and ureters, due to irritation of the saccharine urine.

Atrophy of the testes has been noted by Romberg and Seegen in young men, and recently Hofmeier has reported the case of a young diabetic woman, aged twenty, who came under observation for pruritus vulvæ, in whom the uterus was found small, scarcely 5 cm. (2 inches) long, and the ovaries very much atrophied. As this young woman had no other ailment, the atrophy was ascribed to the diabetes.

Among the most constant secondary lesions is the aggregate of changes known as those of pulmonary phthisis. But a few years ago, when our ideas on this subject were more definite than they are to-day, and when it was thought we had three distinct varieties of phthisis--the tubercular, the catarrhal, and the fibroid--the phthisis of diabetes was regarded as typically catarrhal. At the present time, however, when the tendency at least is to regard all phthisis as tubercular, diabetic phthisis must be consigned to the same category. At the same time, if the tubercle bacillus is to be regarded as the essential criterion of tuberculosis, it must be stated that the diabetic patient is subject to two different lung processes--at least if the observations of Riegel of Giessen are to be regarded as correct. In two cases of diabetic phthisis studied at his clinic, the sputum of one contained numerous bacilli, while the other, although the case presented the most distinct signs of infiltration of the apex, and although more than fifty preparations were investigated, revealed none. The sputum was also said to present some unusual physical characters. So far as I know, no autopsies of cases showing these clinical differences have been reported, although there have been found in diabetes, distinct from the usual cheesy foci, fibroid changes with small smooth-walled cavities. In such cases {203} tubercle bacilli would be absent, while the physical signs of consolidation would be present.

As a part of the phthisical process in diabetes, cavities of various sizes are found and gangrene of the lungs has been observed.

ETIOLOGY.--The problem of the etiology of diabetes mellitus is as unsatisfactorily solved as is that of its pathogenesis. Certainly, a majority of cases of diabetes cannot be accounted for. A certain number may be ascribed to nervous shock, emotion, or mental anxiety; a few to overwork; some to injury and disease of the nervous system; others to abuses in eating and drinking. Among the injuries said to have caused diabetes are blows upon the skull and concussions communicated to the brain, spinal cord, or vaso-motor centres through other parts of the body. Hereditation is held responsible for a certain number of cases. Malarial and continued fevers, gout, rheumatism, cold, and sexual indulgence have all been charged with producing diabetes.

Diabetes mellitus is most common in adult life, although Dickinson reports a case at six years which was fatal, Bence Jones a case aged three and a half, and Roberts another three years old; and in the reports of the Registrar-General of England for the years 1851-60 ten deaths under the age of one and thirty-two under the age of three are included. This statement, in view of the experience of the difficulties of diagnosis in children so young, seems almost incredible. I have never myself met a case in a child under twelve years. At this age I have known two, of which one, a boy, passed from under my notice, while the second, a girl, recovered completely. The disease is most common between the ages of thirty and sixty. The oldest patient I have ever had died of the disease at seventy-two years, having been under my observation for three and a half years.

It is decidedly more frequent in men than in women, carefully prepared statistics of deaths in Philadelphia during the eleven years from 1870 to 1880, inclusive, giving a total of 206 deaths, of which 124, or three-fifths, were males, and 82, or two-fifths, females. This is the experience of all.

My own experience has been singular and interesting. Up to April, 1881, I had never met a case in a woman. Of 18 cases outside of hospital practice which I have noted since that date, 9 were men and 9 women. But I still do not recall an instance of a woman in hospital practice, although I have constantly cases among men.