170 ANATOMY FOR NURSES. [Chap. XIV. 



with usually a little sulphur and sometimes a trace of phos- 

 phorus and iron. They are the only food-stuffs that contain 

 nitrogen in any appreciable quantity, and are sometimes classed 

 as " nitrogenous " food-stuffs. Proteids occur in the form of 

 albumin in the white of egg (egg-albumin), in milk, in blood 

 and lymph (serum-albumin) ; in the form of casein in milk and 

 cheese ; of myosin and sy^itonin in muscle ; of vitellin in tlie 

 yolk of eggs ; of gluten in flour. Allied to proteids but of 

 less nutritive value are the chondrin, obtained from cartilage, 

 and the gelatin, obtained from other varieties of connective 

 tissue, by boiling. 



All proteids yield peptones very readily at the temperature 

 of the body under the action of the acid gastric, and alka- 

 line pancreatic juice. These peptones are highly soluble bodies 

 and readily absorbed. 



The foods that are most rich in the various forms of proteids 

 are meat, milk, eggs, cheese, all kinds of fish, wheat, beans, 

 and oatmeal. 



Fats. — Fats are composed of carbon, hydrogen, and oxygen. 

 They contain on an average in every 100 parts : — 



Carbon 76.5 parts 



Hydrogen 12 " 



Oxygen 11.5 " 



The most important fats are stearin, palmitin, margarin, and 

 olein, which exist in .varying proportions in the fat of animals 

 and vegetable oils, and in milk, butter, lard, etc. The brains 

 of animals and the yolk of eggs contain a complex phosphor- 

 ized fat, called lecithin. Fatty matters are very abundant 

 in olives, sweet almonds, chocolate, castor-oil bean, hemp, and 

 flaxseed. Most of the fatty substances of food are liquefied 

 at the temperature of the body, and are readily oxidized, 

 probably on account of the large amount of carbon which 

 they contain. 



Carbo-hydrates. — In the carbo-hydrates there is sufficient 

 oxygen present to saturate all the hydrogen and to form 

 water ; hence their name. In the fats, there is not quite so 

 much oxygen as hydrogen ; water is, therefore, not formed 

 in them, and in this particular they differ from the carbo- 

 hydrates. 



