The Undertakers' Manual

Section One.

The purpose of the present chapter, so far as our knowledge extends, is to describe the chemical history of those bodies which are characterized as being rather organized than organic; as constituting not merely a product of the vital operations of the being, but the mechanism itself by which these vital operations are carried on; as making part of the tissues essential to its proper organization and life; and as being, while in connection with the animal and participating in its life, protected from the truly chemical reactions of their proper elements, which after the death of the animal, especially when in contact with air or water, rapidly assume simpler forms of union, and breaking up the complex animal tissue into a crowd of binary compounds, under the change well known as putrefaction.

In connection with these substances which form the basis of the organs and tissues of the animal frame, will be brought under survey the processes by which, from the atmosphere or from the materials of our food, the substance of our organs is continually renewed, their growth provided for, and the conditions necessary for the continuance of life and health maintained. The following elucidation of the materials which enter into the composition of the human body is of extreme importance, as it will help to demonstrate why the chemicals employed in the former processes of embalming have been selected in preference to others.

Of Fibrine.—This substance constitutes the basis of the muscular tissue, and forms an important constituent of the blood. In the latter it exists dissolved during life, but separates after death or extraction from the body, producing, with the coloring material, the phenomenon of coagulation. In the muscles the fibrine is arranged in a truly organized and living condition, constituting the contractile fibres, in which it is so interwoven with nervous and vascular filaments as to render its isolation impossible. To obtain pure fibrine, therefore, we have recourse to blood, which, if immediately on being drawn it be briskly agitated with a little bundle of twigs, does not coagulate, but the fibrine is deposited on the twigs in soft, tenacious masses, which, being washed to remove any adhering coloring matter, and digested in alcohol and ether to remove any traces of fatty substances which may adhere to it, constitute pure fibrine; which may be dried by a gentle heat, and appears then as a yellowish, opaque mass, hard, tasteless and inodorous. If it be at all transparent, this results from traces of adhering fat. It is insoluble in water, alcohol and ether; it absorbs, however, so much water as to treble its weight, and thereby recovers the volume, softness and flexibility it possessed before being dried.

If sulphate of soda or nitrate of potash be added to newly drawn blood, its coagulation is prevented; and if fibrine be digested in a strong solution of nitre, it dissolves, forming a thick liquid, which is coagulated by heat, by alcohol, by acids, and is precipitated by the salts of mercury, lead and copper, and by yellow prussiate of potash. This property of fibrine will again come under our notice.

Of Albumen.—This substance is even more extensively distributed through the animal frame than fibrine. Like fibrine, it exists in two conditions, one soluble and one insoluble in water; but whereas the fibrine becomes insoluble almost instantly on being withdrawn from the body, albumen may retain that state for an indefinite time, and its history is therefore more complete. In its soluble form it exists in the blood, in the serous secretions, in the humours of the eye; in the soluble or coagulated form it constitutes a portion of most of the solid tissues.

Soluble Albumen.—This is obtained in the solid form by evaporating to dryness, at a temperature which does not exceed 120°, the serum of blood; the dry mass is yellow, transparent, hard, tough, and contains, besides the albumen, the salts and some other constituents of the blood in minute quantities; these are extracted by digestion in alcohol and ether, which leave the albumen pure. When thus completely dry it maybe heated beyond 212° without passing into the coagulated condition; if digested in cold water it gradually swells up and finally dissolves. This solution, when heated to a temperature between 140° and 150°, coagulates; if dilute, the solution may even be heated to 165° without coagulating, and when present in very small quantity the albumen may not separate until the water boils.

When once coagulated in this manner, albumen is totally insoluble in water; it is then changed into its second form. The solution of albumen is precipitated by alcohol, by acids and metallic salts, exactly as the solution of fibrine in saltpetre; the only distinction that can be drawn between the two is that the saline solution of fibrine is partially decomposed by the addition of a large quantity of water.

The precipitates yielded by a solution of albumen with metallic salts are mixture of two distinct substances, one a compound of albumen with the acid, the other a compound of albumen with the metallic oxide; the former is generally somewhat soluble, the latter insoluble, and hence results the application of albumen as an antidote to mineral poisons, as corrosive sublimate and blue stone.

Albumen is also coagulated by many organic bodies, as tannic acid and creosote, which acts catalytically, as a very minute quantity of it coagulates a large quantity of albumen, without entering into combination with it.

Of the Gelatinous Constituents of the Tissues.—When the skin, cellular or serous, tissues, tendons, and some forms of cartilage, as that of bones, are boiled in water, they dissolve in great part and form a solution which gelatinizes on cooling. Some of these tissues, as the skin, dissolve easily and almost completely; others dissolve but partly, and leave behind a quantity of coagulated albumen. In most kinds of cartilage a very prolonged boiling is necessary to extract a sensible quantity of gelatine. These various tissues are thus found to consist of albumen and gelatine, united in various proportions, and each presenting various degrees of condensation of texture; but by boiling they may be completely separated from each other.

Gelatine is insoluble in alcohol and ether. When a solution of gelatine is long exposed to the air, it undergoes a commencement of putrefaction, and loses its property of gelatinizing.

The action of reagents on gelatine is in some cases of high interest, it is not precipitated by solutions of either ordinary or basic alum, but if a solution of common salt be also mixed, the gelatine falls down, combined with alumina, as it decomposes the muriate of ammonia which is then formed. On this principle is founded the manufacture of white leather, by a kind of tanning with alum.

The most important compound of gelatine is that with tannic acid, which constitutes ordinary leather; this reaction is so distinct that one part of gelatine in five thousand of water is at once detected by the infusion of galls.

Many chemists consider that gelatine is merely a product of the decomposition of albumen and fibrine by boiling water, and not a true constituent of the tissues; but this idea is thought to be incorrect, on the following grounds: First, pure fibrine or albumen gives no gelatine by boiling; second, in the process of tanning, the tannic acid combines with gelatine in a skin which has never been boiled; and third, that we can easily understand why some tissues give more gelatine than others by the different degrees of condensation of their structure. But it is rather considered that gelatine bears the same relation to the tissues of the skin or cellular membrane that protein does to the fibrine of the blood, being really a product of its death and decomposition, though the only representative of it which we can have.

Of the Fatty Constituents of the Tissues.—The fatty bodies, although contributing essentially to the support of the animal frame, are mere secretions, and do not form any portion of its organized tissues. The substances properly included under the present head are the constituents of the nervous tissue, such as it is found in the brain, the spinal cord and the nerves.

In the composition of the brain, it is easy to distinguish three, perhaps five, distinct substances of a fatty nature; the most characteristic and important is called cerebrote; in composition it resembles albumen, containing a large quantity of nitrogen.

Saline, and Extractive Constituents of the Tissues.—We find in all the animal tissues small quantities of a great variety of salts, the same as those which will be hereafter noticed as existing in the blood, to the presence of which in the substance of the tissues they are probably due. In the tissue of the bones and teeth, however, these saline matters are deposited in much greater quantities, and in disease and old age bony deposits occur in all those tissues, which yield true gelatine on boiling. The composition of the bones will be hereafter noticed.

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