714 PHYSIOLOGY OF DIGESTION AND SECRETION. 



it for rapid absorption, and the name of peptone was given to it. It 

 was quickly found, however, that the process is complicated that in 

 the conversion to so-called "peptone" the protein under digestion 

 passes through a number of intermediate stages. The intermediate 

 products were partially isolated and were given specific names, such 

 as acid-albumin, parapeptone, and propetone. The present concep- 

 tion of the process we owe chiefly to Kiihne. This author believed 

 that the protein passes through three general stages before reaching 

 the final condition of peptone. This view is indicated briefly by the 

 following schema : 



Native protein. 



Acid albumin (syntonin). 



Primary proteoses (protalbumoses). 



Secondary proteoses (deutero-albumoses). 



Peptone. 



The first step is the conversion of the protein to an acid albumin. 

 This change may be considered as being chiefly an effect of the hy- 

 drochloric acid, although in some way the combined action of the 

 pepsin-hydrochloric acid compound is more effective than a solution 

 of the acid alone of the same strength. Like the acid albumins in 

 general (see appendix), the syntonin is readily precipitated on 

 neutralization. In the beginning of peptic digestion, therefore, 

 if the solution is neutralized with dilute alkali, an abundant precipi- 

 tate of syntonin occurs. Later on in the digestion neutralization 

 gives no such effect the syntonin has all passed into a further stage 

 of digestion. Under the influence of the pepsin the syntonin under- 

 goes hydrolysis, with the production of a number of bodies which 

 as a group are designated as primary proteoses or protalbumoses.* 

 Although several members of this group have been isolated and given 

 separate names, so much doubt prevails as to the chemical individ- 

 uality of these substances that it is best perhaps to regard them as a 

 group of compounds which under the continued influence of the 

 pepsin undergo still further hydrolysis with the formation of secon- 

 dary proteoses or deutero-albumoses. As compared with the primary 

 proteoses, the secondary ones are distinguished by a greater solu- 

 bility ; they require a stronger saturation with neutral salts to precipi- 

 tate them. (See Appendix.) The secondary proteoses undergo still 

 further hydrolysis, with the production of peptone, or perhaps it 

 would be better to say peptones. The peptones show still greater 

 solubility, and, in fact, peptone, in Kiihne's sense, is that compound 

 or group of compounds formed in peptic digestion which, while still 

 showing protein reactions (biuret reaction), is not coagulated by 



* The products intermediate between the original protein and the pep- 

 tone are described in general as albumoses or as proteoses, according as one 

 takes the term protein or albumin as the generic name for the original sub- 

 stance. The term protein is generally used in English ; hence, the intermedi- 

 ate products are more appropriately designated as proteoses. 



