Sept. 17, 191 7 



Proteins of Certain Insects 



635 



selected for comparison because they represent the more common higher 

 types of animal proteins. 



Table I. — Percentage of amino-acid groups in animal proteins from different sources 



Group. 



Ammonia nitrogen 



Melanin nitrogen 



Arginin nitrogen 



Histidin nitrogen 



Cystin nitrogen 



Lysin nitrogen 



Amino nitrogen (in filtrate from bases). . 



Non-amino nitrogen (in filtrate from 



bases) 



Total 



Grass- 

 hoppers. 



9. 14 



3-42 



14.98 



5.62 



•23 



8.04 



52.87 



4-32 



98.62 



Jttne bugs. 



8.96 

 6.78 



"•53 



6-57 



•35 



8.02 



50.80 



Beef roast. 



3.85 



3-27 

 5. 22 



15-44 



13-34 



•49 



8. 40 



40. 89 



9-38 



96- 43 



Turkey 

 white meat. 



5-05 



I. 72 



14. 72 



18.23 



•47 



7.67 



42.41 



7. 26 



98.13 



As a whole, the results show considerable similarity for proteins vary- 

 ing so widely in their sources of origin. The chief points to be taken into 

 consideration in an analysis of this kind, as showing important points 

 in similarity or differences, are the four amino-acid groups, arginin, 

 histidin, cystin, and lysin. In the arginin determinations very closely 

 agreeing results have been obtained on each of the different proteins 

 analyzed. In the histidin determinations there is considerable variation. 

 The result for this giotip in the first and second analyses is one-half of 

 that in the third and one-third of that obtained in the fourth analysis. 

 Figures for the cystin group show an increase of one-half in the second 

 analysis over the first, and more than twice as much in the third and 

 fourth analyses as in the first. The determinations in the lysin group 

 show a remarkably close agreement in all the analyses. In the light of 

 our present knowledge" this is by far one of the most important groups 

 contained in proteins, from the standpoint of growth and nutrition. 



For the purpose of showing further points of interest in connection 

 with the grasshopper the following work was carried out: 



On September 23, 191 6, about 200 gm. of grasshoppers were caught, 

 killed by means of potassium cyanid, dried at 100° C. until free from 

 water, ground in a mortar, and placed in a ground-glass-stoppered bottle. 

 With the exception of the opening of the bottle for weighing out por- 

 tions for protein, fat, and mineral-constituent determinations, the material 

 has remained in the laboratory unmolested until the present time. A 

 protein determination made recently on the same material after stand- 

 ing in the laboratory in this condition for seven months shows that there 

 has been no alteration in the protein content during this period of time, 

 which demonstrates that the dry material can be kept indefinitely. 



