746 



PHYSIOLOGY 



experiments made by Friedlander the absorptions of various proteins were 

 compared after their introduction into loops of the small intestine which had 

 been washed free from ferment. During a period of three hours this author 

 found that 21 per cent, of the proteins of egg white or of blood serum were 

 absorbed. During the same period, of alkali- albumen which had been intro- 

 duced into the loops, 69 per cent, was absorbed. On the other hand, when 





FIG. 352. Figures (from RETJTER) showing changes in intestinal epithelium 



induced by absorption of protein. 



I, epithelium of fasting rat ; II, initial stage ; III, later stage of protein 



absorption. 



syntonin and casein were introduced into the intestine, no absorption what- 

 ever was observed. As to the condition in which such unchanged protein 

 reaches the blood stream our knowledge is still imperfect. Foreign proteins, 

 such as egg albumin, or the serum of other species introduced into the blood 

 stream, may cause poisonous effects, and give rise to albuminuria, to lowering 

 of blood pressure, or to alteration of the coagulability of the blood. If 

 injected in small quantities they excite, as a reaction on the part of the 

 organism, the production in the blood serum of a precipitin, and the presence 

 of the precipitin may be looked upon therefore as a test by which we may 

 decide whether these proteins have passed through the intestinal wall 

 unchanged. In most cases it is found that, however abundant the amount 

 of protein administered in the soluble form, none of it appears in the urine, 



