168 ANIMAL AMIDES. 



know whether they ought to be placed among animal acids or 

 bases, or whether they are not rather indifferent substances. The 

 last supposition accords best with the present state of our know- 

 ledge. They have a strong analogy to the amides from the ve- 

 getable kingdom ; the account of which will be found in the 

 Chemistry of Vegetable Bodies, p. 590. For this reason they 

 have been placed together under that provisional denomination. 

 They may be arranged under the following heads : 

 I. Protein. II. Gelatin, 



(1.) Albumen. (1.) Collin. 



(2.) Albumen from silk. (2.) Chondrin. 



(3.) Casein. (3.) Gelatin from silk. 



(4.) Fibrin of blood. III. Hematosin 



(5.) Fibrin of silk. IV. Spermatin. 



(6.) Ricotin. V. Salivin. 



VI. Pepsin. 

 VII. Pancreatin. 

 These will be the subject of the seven following chapters. 



CHAPTER I. 



OF PROTEIN. 



THIS name was given by Mulder to a substance which consti- 

 tutes the bases of albumen, fibrin, flesh, casein, and probably of 

 other animal tissues.* To obtain it, albumen from eggs or blood 

 may be taken and digested in water, alcohol, and ether, till every 

 thing soluble in these liquids has been removed. It is then 

 treated with dilute muriatic acid, which removes the insoluble 

 earthy salts, especially phosphate of lime. It is then to be dis- 

 solved in a moderately strong alkaline ley, and the solution must 

 be heated to 122, by which a little phosphate of potash and sul- 

 phuret of potassium are formed, originating from sulphur and 

 phosphorus existing in the albumen in an unoxydized state. 

 The protein thus treated is precipitated from its alkaline solu- 



* So named from av*Ti/. I am first. 

 3 



