10 .1 Manual of Veterinary Phy&iology. 



Albuminoids are substances closely allied to albumins, but 

 differing- from them in some important particulars ; they 

 consist of such substances as gelatin, chondrin, mucin, 

 elastin, keratin, and many others. These pass through the 

 proteose and peptone stage in the same way as true albumins, 

 but with certain differences. 



The ordinary Tests for Proteids are based upon their pre- 

 cipitation by certain reagents, and in the same way it is 

 possible to distinguish between one proteid and another. 

 The most common test is the so-called xanthoproteic, ob- 

 tained by the addition of a drop or two of nitric acid which 

 produces a precipitate increased by boiling and turned 

 yellow ; albumoses are rendered clear by boiling with nitric 

 acid and are thrown down again on cooling. If to the 

 yellow fluid obtained by the action of nitric acid on an 

 albuminous body a little ammonia be added, an orange 

 colour is produced. Professor Halliburton regards this re- 

 action as one of the most delicate we possess for proteids, 

 we need hardly, therefore, go further than this for a test, 

 although there are many other acids, organic and inorganic, 

 salts of metals, neutral salts, etc., which act as precipitants. 

 and to which reference will be found in text-books devoted 

 to physiological chemistry; attention need here only be 

 drawn to the fact that we are able to distinguish between 

 serum albumin and globulin, and are also capable of separat- 

 ing peptones from other proteids, by the action of mag- 

 nesium sulphate and ammonium sulphate. 



A very remarkable fact about proteid substances is that 

 though they constitute the mainspring of organic life, yet 

 they number amongst them, or amongst their decomposi- 

 tion products, some of the most powerful poisons known. 

 Snake poison is a proteid, and even the albumose formed 

 during the peptic digestion of albumin is highly poisonous 

 if injected into the circulation. 



The Ferments come under the proteid classification : they 

 are bodies possessing the most remarkable activity, and 

 capable of inducing in other bodies with which they may 

 be brought into contact, changes which result in the pro- 



