38 HUMAN PHYSIOLOGY 



except tannic and phosphotungstic acid. They are more 

 dialyzable than the albumoses, yet their power of dialyzing 

 is only one-fourth of that of grape-sugar. They are solu- 

 ble in all proportions in water. Their solutions have a dis- 

 agreeable bitter taste. 



The red color which peptones give in the biuret reaction 

 is highly characteristic of peptones, the other proteids giving 

 a reddish-violet color. 



The various peptones differ from each other in the amount 

 of sulphur ; some have loosely combined sulphur, others have 

 only firmly combined sulphur. They also differ in their 

 behavior towards the pancreatic ferment trypsin ; the ' ' hemi- 

 peptones ' ' are split by trypsin into leucine, tyrosine, and 

 aspartic acid, etc. ; the " anti- peptones " not. 



Nothing is definitely known as to the number of peptone mole- 

 cules formed from one molecule of simple proteid. From a 

 molecule of crystallized serum albumin, if the calculated molecular 

 weight, 17,070, is correct, at most ten molecules of peptones can 

 be formed, for one molecule of serum albumin contains ten atoms 

 of sulphur and each molecule of peptone must contain at least one 

 atom of sulphur, since peptone must still be regarded as a proteid. 



Albumoses and peptones are found only in the alimentary 

 canal, having been produced by the digestion of the proteids 

 of the food. By their formation, the insoluble and coagu- 

 lable or at least undialyzable proteid of the food is rendered 

 into a soluble and dialyzable form suitable for absorption. 



Proteoses-like bodies are also formed from native proteids by 

 the action of superheated steam. The products thus formed are 

 called atmidalbumoses and atmidpeptones. They have no loosely 

 combined sulphur and differ from the ordinary proteoses in their 

 precipitation. Atmidproteoses are not readily absorbed from the 

 intestine. Evidently by superheated steam the proteids are not 

 only split up but undergo other changes which make^ them more 

 or less unsuitable for nutrition. 



IV. Albuminoids are derivatives of proteids, which still 

 have the characteristic percentage composition of proteids, 

 but differ from them chemically, physically, and especially 

 physiologically. Some of the albuminoids contain more 

 sulphur, others less, than the proteids. They do not give 



