3 82 HUMAN PHYSIOLOGY 



By assimilation is meant the taking of the food con- 

 stituent from the blood by the muscle and other tissues so 

 that it may be used, for until the constituents of the food 

 have become part of the protoplasm of the tissues they 

 are not oxidised. Apparently the only substances which 

 can be freely assimilated and used by the tissues are the 

 three proximate principles of the food, although alcohol and 

 possibly some other similar substances may be utilised to a 

 small extent. 



Y. The subject of Dietetics cannot be left without allud- 

 ing to the influence of two very universally used materials 

 alcohol and tea. 



Alcohol. The influence of alcohol may be considered 

 under two heads. 



1st. Before absorption. Moderate doses of alcohol taken 

 along with food do not appear to interfere with the digestion 

 and absorption of proteids, of carbohydrates, or of fats. 

 When taken apart from food and in such excessive doses 

 as to act as an irritant and to cause catarrh of the 

 alimentary canal, alcohol of course has a prejudicial 

 influence. 



2nd. After absorption. The tissues have the power of 

 oxidising a small quantity of alcohol, and since the com- 

 bustion of 1 grm. of alcohol liberates 7'06 Calories of energy, 

 alcohol must be regarded as a food just in the same way as 

 sugar is a food. The amount of alcohol which can be thus 

 oxidised varies in different individuals, but the average 

 man cannot use more than 50 grms. per diem. Any 

 alcohol taken above the amount which can be oxidised is 

 excreted in the urine and breath, and in its passage through 

 the body it acts as a poison to the protoplasm, first diminish- 

 ing its activity and so diminishing the rate of waste, and 

 secondly causing the death of the protoplasm and the 

 removal of the broken-down nitrogenous constituents in the 

 urine. Its poisonous action on the liver is demonstrated 

 by the diminished building up of urea, so that a greater 

 quantity of waste nitrogen is excreted in other forms. In 

 moderate doses it stimulates the heart and dilates the 

 arterioles. Its first action in checking the activity of meta- 



