COMPOSITION AND PROPERTIES OF GELATINE. 123 



141. The composition of the White .fibrous tissues is very different from 

 that of most others ; for they yield to boiling water the substance called 

 Gelatine, which does not seem capable of the same degree of organization 

 with the Proteine-compounds. This may be obtained by boiling portions of 

 Skin, Areolar tissue, Serous membrane, Tendon, Ligament, &c., in water, for 

 some time ; after which the decoction is allowed to cool, when it solidifies 

 into a jelly of greater or less thickness. Some tissues dissolve readily in this 

 manner, and little residual substance is left; this is especially the case with 

 areolar tissue, serous membranes, and (in a less degree) with skin. Others 

 require a long boiling for the extraction of any Gelatine ; and even then it is 

 obtained in but small quantity ; of this kind are the Elastic fibrous tissue, 

 and some forms of Cartilage. A peculiar modification of this principle 

 exists in most of the permanent cartilages ; and has received the name of 

 Chondrine. Gelatine is not found in the blood, nor in any of the healthy 

 fluids ; and some Chemists are of opinion, that it is rather a product of the 

 operation practised to separate it, than a real constituent of the living solids. 

 This idea seems inconsistent, however, with the fact, that the gelatinous tis- 

 sues will exhibit, without any preparation, the best marked of the chemical 

 properties which are regarded as characteristic of Gelatine, that, namely, of 

 forming a peculiar insoluble compound with Tannin ; and the Tanno-Gelatine, 

 which may be obtained by precipitating Gelatine from a solution, and that 

 which results from the action of Tannin on Animal membrane, appear to be 

 precisely analogous in every respect, save in the presence of structure in the 

 latter, which is absent in the former. Moreover, the Gelatinous tissues are 

 found, when submitted to ultimate analysis, to possess exactly the same com- 

 position with Gelatine itself. Still it seems probable, that the arrangement of 

 the component particles is in some degree altered by the process of boiling ; 

 for it is found that, the more distinct the fibrous structure of the tissue, the 

 less it is affected by the prolonged action of cold water, and the longer it must 

 be boiled, before it is resolved into Gelatine. 



a. Gelatine is very sparingly soluble in cold water ; by contact with which, however, it is 

 caused to swell up and soften. It is readily dissolved by hot water ; and forms so strong a 

 jelly on cooling, that 1 part in 100 of water becomes a consistent solid. Its reaction with 

 Tannic acid is so distinct, that 1 part in 5000 of water is at once detected by infusion of 

 Galls. The following are the results of four analyses of Gelatine by Scherer and Mulder. 



SCHERER. MULDER. 



Carbon . . . 50'557 50-774 50-048 50-948 



Hydrogen . . 6-903 7-152 6-477 6-643 



Nitrogen . . 18-790 18'320 18-350 18-388 



Oxygen . . 23-750 23-754 25-125 24-921 



The formula deduced by Mulder from this composition, and from the combinations of 

 Gelatine with Tannic and Chlorous acids, is 13 C, 10 H, 2 N, 5 O. When Gelatine is boiled 

 for some time, it loses its power of forming a jelly on cooling ; and it is stated by Mulder, 

 that this is due to its union with an additional amount of water, a true Hydrate of Gelatine 

 being formed by the combination of 4 Equiv. of Gelatine, with 1 Equiv. of Water. The 

 same product is obtained by adding Ammonia to the Chlorite of Gelatine, and removing by 

 Alcohol the Sal Ammoniac thus formed. 



b. It is not yet known how Gelatine is produced in the Animal body. There cannot be 

 a doubt that it may be elaborated from Albumen ; since we find a very large amount of it 

 in the tissues of young animals, which are entirely formed from albuminous matter ; and 

 also in the tissues of herbivorous animals, which cannot receive it in their food, since Plants 

 yield no substance resembling Gelatine in composition. It has been suggested by Mulder, 

 that Gelatine may be formed by the decomposition of Proteine, which has been already 

 mentioned as taking place from the agency of weak alkaline solutions ( 116 6), and which 

 must probably, therefore, be continually occurring in the Blood. For, if to each atom of Pro- 

 tid and Erythioprotid, we add one of the atoms of Ammonia which are given of in that 



