ELEMENTAEY PHYSIOLOGICAL CHEMISTRY 



229 



EXPERIMENT VII. Examine the crystals of tyrosin under the micro- 

 scope, and note that they consist of fine needles grouped into star- 

 shaped masses (Fig. 148). 1 



FIG. 148. Crystals of leucin and tyrosin. 



There are no other important amido acids till we come to the 

 member of the series which contains six carbon atoms. This is amido 

 caproic acid or leucin. 2 



CH 3 CH 2 CHg CH 2 CH<^pQ ATT 

 EXPERIMENT VIII. Examine the crystals of leucin under the micro- 



1 A body very closely related to tyrosin in its chemical structure has recently 

 been described amongst the products of hydrolysis of proteids by acid. This is 

 phenylalanin, differing from tyrosin only in that it does not contain an - OH 

 group. It has also been discovered in the products of the prolonged action of 

 pepsin on proteids. 



2 It has recently been shown, however, that the true constitution of leucin is 

 rather a amido isobutylacetic acid 



