304 AGRICULTURAL EXPERIMENT STATION. [Jan. 



other hand, was nearly all dissolved by the pepsin solution. 

 As soon, however, as the leathers were submitted to the ac- 

 tion of the pancreas solution a decided change was noted ; 

 the solution became quite dark in color and the larger part 

 of the leather went into solution. While this method indi- 

 cated a greater availability on the part of the sole-leather 

 after it had been submitted to steam 2)ressure, it nevertheless 

 did not give a correct idea of the digestibility and conse- 

 quent availability of the leather when compared with the 

 dried blood. 



The substances were therefore submitted to the action of 

 the pepsin solution alone, with results as follows : — 



These results coincide very closely with those obtained by 

 other investigators. The sole-leather itself proved very in- 

 digestible. It is possible that it might have proved some- 

 what less so if no hydrochloric acid had been added during 

 the digestion.* The sole-leather after being subjected to the 

 action of the steam pressure had a digestibility of 34.40 per 

 cent., which coincides with results obtained by others for 

 prepared leather, as the following samples show : — 



Percentage of Nitro- 

 gen digested. 



Leather cooked and roasted (Stutzer), . . . .39.19 



Roasted leather meal (Shepard and Chazal), . . 37.80 



Leather by benzine process (Johnson), . . . .35.90 



Leather by superheated steam (Johnson) , . . .33.30 



"While, then, the action of steam and heat renders the 

 leather somewhat more digestible and probably more avail- 

 able in the soil, it still has a digestibility below 50 per cent. 

 Only the very poorest kinds of animal matter reach this low 

 figure (50). The so-called Philadelphia tankage was also 

 below 50 per cent, digestible, and may be classified with. 



* Connecticut Experiment Station, 1886, page 122. 



