36 HISTOLOGY. 



sides forming a constituent of milk, casein is found in blood, saliva, bile, 

 and the lens of the eye. 



4th. Pepsin. This substance was discovered by Schwann, and analysed 

 by Vogel, who found it to be composed of C^ H^ N 8 O 1(? . It is so 

 much like albumen that it is difficult to discover a distinction between 

 them. It is found in the gastric glands. 



5th. Globulin (Pr 15 -f S) exists in the blood corpuscles; very like albu 

 men. 



6th. Spermatin is found in semen ; probably fibrin, altered and filled 

 with living forms. 



7th. Mucus consists of globules floating in a clear fluid, the constitution 

 of each being different. 



8th. Keratin (Pr S 2 ). The product of the analysis of hair, cuticle, &c. 



9th. Salivin. Found only in the saliva. 



Besides the protein compounds thus enumerated, we have the extractive 

 matter, obtained by either water or alcohol from muscular flesh. 



The watery extract is called osmazome, is highly volatile, gives the 

 taste and odour to soups and roast meats, and is no doubt a product of 

 the treatment of the meat, or a new combination of the animal elements 

 occurring during the effort to procure it. 



Gelatine is another substance obtained from portions of the animal 

 body, and differs according to the tissue which furnishes it. Thus ten- 

 dons, ligaments and bone furnish colla, or glue, which consists of C 52 

 HJO N 8 Ogo ; whilst the cartilages and the cornea furnish cho-ndrin, the 

 composition of which is N^ H 26 N 4 O u . 



Hematin is found in C 41 H^ N 3 6 united w r ith a little iron, \vhich is 

 not essential to its composition or existence. 



A number of principles have been described as existing in the hepatic 

 secretion or bile, but much research is yet necessary to clear up the con- 

 fusion which exist in writings with regard to them. They may be enu- 

 merated : Bilin, fellinic acid, cholinic add, taurin, dyslysin, cholepyrrhin, 

 biliphcdn, biliverdin, bilifulvin, cholesterin, oleate, mangarate, and stearate 

 of soda, chloride of sodium, sulphate, phosphate, and lactate of soda, and 

 phosphate of lime. 



Urea and uric acid, found in the urine, should not be considered as 

 constituent parts of an animal, but as elements combined in a particular 

 way for the purpose of being excreted. 



II. The NON-NITROGENIZED COMPOUNDS, found in the bodies or secretions 

 of animals, are not numerous. When milk is dried, two-fifths of its solid 

 contents consist of a peculiar sugar, called saccharum lactis, and composed 

 of Qs H 4 4 +HO. It crystallizes in four-sided prisms, and has a sp. gr 

 of 1.543. 



It also contains an acid called lactic (C 6 H 5 5 ), common in all the 

 fluids and secretions of the body, and united in them with either potash 

 soda, ammonia, lime, or magnesia. 



Fat consists of cells held together by areolar tissue and vessels, and is 

 found by the chemists to contain glycerin, stearic acid, margaric acid, and 

 elaic acid, all of which are destitute of nitrogen. 



The solidity of the fat of an animal depends upon the proportion of the 

 above ingredients ; thus, when stearic acid preponderates, the fat is solid, 

 and when elaic, fluid. 



