98 PHYSIOLOGY FOR DENTAL STUDENTS. 



above mentioned, with zein of corn. It will be seen, there- 

 fore, that of the two proteins in wheat one, glutenin, contains 

 all the necessary units for building up the growing tissues, but 

 that in the other protein, gliadin, some essential unit is absent ; 

 by analysis this was found to be lysin. By adding lysin to 

 gliadin a normal curve of growth resulted, thus showing that 

 this was really the missing unit. The result was made even more 

 spectacular by feeding a batch of young rats on gliadin alone, 

 so that they remained undeveloped and stunted, and then adding 

 lysin to their diet, when they very quickly made up for lost time, 

 and soon reached, if not quite, yet almost as good a development 

 as their more fortunate brothers who had been fed on glutenin 

 or casein from the very start. 



The animal economy itself can therefore produce certain of 

 the amino bodies thus, as we have seen, it can produce glycin 

 this power being much more developed in the case of herbivor- 

 ous as compared with carnivorous animals. In the vegetable 

 food on which oxen live several of the prominent amino bodies of 

 muscle protein are missing, but they are constructed in the or- 

 ganism by altering the arrangement of the molecules of those 

 amino bodies which are present, so that a protein is built up 

 which is very like that present in the tissue of the carnivorous 

 animals. Even in the case of the herbivora, however, there are 

 limitations to the power of forming new amino bodies. Trypto- 

 phan cannot be formed in this way, for example. 



