ELEMENTS OF COMPOSITION. 



23 



genous glycosid, giving some indication as to the constitution of the 

 albuminates. With sulpnuric acid chondrin only yields leucin appa- 

 rently. Of cliondrigen but little is known. 



As to the origin of chondrin from the protein substances, the same 

 may be said as of glutin. In regard, however, to a transformation of 

 chondrin into glutin during the process of ossification, spoken of by some, 

 but rather improbable, the present state of chemistry permits of no 

 definite conclusions being drawn. 



It would appear that other matters nearly related to these two better 

 known glue-yielding substances may also cccur in the body. 



Elastic Material, Elastin. 



In numerous tissues of the body a substance destitute of sulphur is 

 met with, which, unlike the glutin-yielding materials, is remarkable for 

 its great insolubility and unchangeableness. 



This elastic substance, even on prolonged boiling, yields no glutin, if 

 completely free from connective tissue. It is likewise unaffected by 

 acetic acid, whether warm or cold. It may be dissolved, however, by a 

 boiling concentrated solution of caustic potash, and by cold sulphuric 

 acid; also gradually, by saturated nitric acid with the formation of xantho- 

 proteinic acid. Elastin is not coloured red by the test of sulphuric acid 

 and sugar. As decomposition products under the action of the last-named 

 acid, we find leucin, but neither tyrosin nor glycin. 



Elastin, the definition of which presents many difficulties also to the 

 microscopist, enters into the formation of fibres, plates, and limiting 

 layers in connective tissue. It forms also in various organs possibly, 

 both follicles and tubes, and capsules around animal cells, without being a 

 constituent of the true cell-body itself. 



The great unchangeableness of this substance, with its chemical inert- 

 ness, seem to render it peculiarly fitted to include the fluids of the system, 

 and to act at times as a filter for the same. Its great elasticity also 

 serves many purposes. 



Its source is not as yet known with any degree of certainty. There 

 can be hardly any doubt however that it has its origin from the protein 

 compounds of the body. 



D. The Fatty Acids and Fats. 



Fatty acids appear in our body either free or combined with an 

 inorganic base (fat-soap), or as a mixture of glycerin-ethers (neutral fats). 

 Let us glance for a moment at the latter : 



c* 



(OH 



Glycerin, C 3 H 8 3 or C 3 H 5 j OH 

 i OH 



( OH, 



Glycerin, a triatomic alcohol, with the radicle glyceryl = C 3 H 5 , is met 

 with as a colourless, non-crystallizable syrup, miscible with water in all 

 proportions. 



Before going further, let us consider for a, moment glycerophosphoric 

 3 



