68 The Feeding of Animals 



carbohydrate (animal gum). The fact of such a union 

 is demonstrated by boiling mucin with an acid when 

 an acid albuminate and carbohydrate -like body are 

 produced. The mucin-like bodies are not especially 

 important in nutrition. 



The blood contains a modified proteid which has an 

 importance second to none in its relation to the nu- 

 tritive processes. Reference is made to haemoglobin, 

 which arises from the union of an albumin called 

 globin arid a coloring matter (pigment) called ha3tna- 

 tin. The latter is peculiar in containing iron. The 

 especial function of haemoglobin is as a carrier of oxy- 

 gen, and it is enabled to do its work through the 

 property of taking in and releasing oxygen with great 

 readiness. This action will be discussed later when 

 we consider respiration. 



The yelatinoids. It is a matter of common obser- 

 vation in cookery that when meat containing tendons 

 (cartilage) or bones is submitted to the action of 

 boiling water there is obtained in the extract a sub- 

 stance, which, especially when it is cold, we recognize 

 as the one known as gelatine. Gelatine as such is not 

 found in the animal tissues, but is derived from certain 

 constituents of the connective tissues like the collagen 

 of tendons and of bones, that from the latter source 

 being also known as ossein. Collagen is undoubt- 

 edly transformed into gelatine by taking up water. 



Gelatine is insoluble in cold water, but dissolves 

 in hot. As the dry commercial article, it is a tena- 

 cious substance which, when prepared in thin layers, 

 is transparent. When collagen is acted upon by tan- 



