COLLAGEN. CHONDRINE. 91 



sodium chloride, filtering the expressed liquid, and then precipitating 

 the dissolved myosine by dropping the clear solution into distilled 

 water. It may also be precipitated by adding sodium chloride in sub- 

 stance, and thus increasing the strength of .the solution. Myosine is, 

 distinguished from the fibrine of the blood by its complete solubility 

 in saline solutions of a certain strength, as well as in dilute acids and 

 alkalies. When dissolved in a neutral saline fluid it is coagulable by 

 heat, like the albumen of blood. 



The preceding substances are all naturally liquid, or nearly so, in con- 

 sistency, and form constituent parts of the various animal fluids and 

 juices. The following are ingredients of the solid tissues. 



Collagen. 



This substance is very widely diffused in the animal body, forming 

 the more or less homogeneous interstitial mass of the bones, perios- 

 teum, tendons, ligaments, fasciae, and connective tissues generally. All 

 these tissues, although at first insoluble, after long ebullition dissolve 

 in the boiling water ; and the substance thus dissolved solidifies on cool- 

 ing into a jelly-like mass. This substance is gelatine, or the animal 

 principle of glue. Gelatine, however, does not exist as such in the 

 osseous and fibrous tissues in their natural condition, but is evidently 

 the result of a transformation produced by long boiling. The original 

 body of which these tissues are mainly composed is termed "collagen ;" 

 that is, a substance which produces gelatine or glue. The conversion 

 of collagen into gelatine is a simple transformation, and neither a decom- 

 position nor combination, since it is not accompanied by any increase or 

 diminution of weight. 



The gelatine produced by the action of boiling water on collagen, 

 when present in the proportion of ten parts per thousand, solidifies on 

 cooling ; below this proportion, or if the boiling be repeated, it may 

 remain liquid. Its solution rotates the plane of polarization to the 

 left 130. It is precipitated by alcohol and by tannic acid. The last, 

 which is the only acid by which this substance is precipitated, is a 

 very sensitive test of its presence ; and, according to Hardy, 1 will de- 

 tect one part of gelatine in 5000 parts of water. A similar combination 

 no doubt takes place, in the process of tanning, between tannic acid 

 and the original collagen of the fibrous tissues, by which they are ren- 

 dered harder, more impermeable to water, and incapable of putrefac- 

 tion. Gelatine is not affected by potassium ferrocyanide with acetic 

 acid, nor by lead subacetate. 



Chondrine. 



The amorphous intercellular substance of cartilage resembles that 

 of the bones and the fibrous tissues in being changed by prolonged boil- 

 ing with water into a substance which will gelatinize on cooling. In 



1 Chimie Biologique. Paris, 1871, p. 282. 



