THE VOLATILE PART OF PLANTS. 101 



teoses (albumoses, caseoses, ghbuloses, etc.) ; those last 



produced they designate peptones, but investigators are 



not as yet agreed as to the precise application of these 



terms. What have been formerly called peptones are 



now considered to be largely proteoses. 



The composition of some of these bodies may be seen 



from the following analyses by Chittenden and Painter : 



c. H. N. s. o. 



Casein 63.30 7.07 15.91 0.82 22.03 



Protocaseose 52.50 7.16 15.73 0.96 23.86 



Deuteiocaseose 51.69 6.98 15.73 0.75 25.03 



Casein-Peptone 49.94 6.81 16.30 0.68 26.57 



Of the several products which have been analyzed and 

 classed as proteoses and peptones, it is not certain that 

 any one is a strictly homogeneous substance. It is more 

 than probable that some of them are mixtures. The 

 proper use of these names is provisional, to characterize 

 certain evidently distinct stages of albuminoid metamor- 

 phosis, whose •exact nature can only be cleared up by 

 further investigation. 



The peptones may be defined as the final products of 

 the action of the peptic ferment. I'hey are soluble in 

 water and freely diffusible through animal membranes. 

 The albumoses (or proteoses) are intermediate between 

 the albuminoids and the peptones, being mostly soluble 

 in water but not freely diffusible. 



The proteoses much resemble the albuminoids from 

 which they are deiived, not only in composition, but in 

 many of their properties. The peptones have less re- 

 semblance, but appear capable of partially reverting to 

 proteoses, as some of the latter are said to yield coagula- 

 ble albuminoids when kept in the moist state. 



Weak acids and alkalies also convert the albuminoids 

 into proteoses and peptones, and probably the acid-pro- 

 teids, perhaps also the alkali-proteids, already mentioned, 

 contain proteoses in admixture. Since pepsin-digestion 

 requires the aid of a free acid and trypsin-digestion sue- 



