CHEMICAL BASIS OF THE ANIMAL BODY. 35 



proteids contained in the aleurone-grains of plants are exceedingly 

 resistant to this coagulating action of alcohol 1 . 



CLASS VI. Albumoses and Peptones. 



When any of the proteids already described are submitted to the 

 digestive action of pepsin or trypsin, certain substances are formed, in 

 the earlier stages of the action, which are intermediate between the 

 proteid undergoing digestion and the proteid product (peptone) which 

 finally results from the action of the enzymes. When the digestive 

 fluid employed is pepsin in presence of dilute (-2 p.c.) hydrochloric 

 acid, a small portion of the proteid may be at first converted into a form 

 of ordinary acid-albumin 2 . It is obtained by neutralising a peptic 

 digestive mixture at an early stage of the digestion, and has been 

 frequently and almost usually confounded with the * parapeptone ' of 

 Meissner. As will be explained later on, the two substances are quite 

 distinct forms of proteid. At a later stage of the digestion the first- 

 formed acid-albumin disappears, a considerable amount of parapeptone 

 is formed and other products make their appearance, which are known 

 collectively under the name of albumoses 3 . By a more prolonged 

 action of the pepsin a considerable portion of these albumoses is 

 further changed into the final product peptones 4 ; beyond this stage 

 no further change can be brought about by the action of pepsin. If 

 trypsin be employed in an alkaline solution (*25 p.c. Na 2 CO 3 f the 

 decomposition of the proteid is much more complicated and profound. 

 Instead of acid-albumin a small amount of alkali-albumin makes its 

 appearance, together with more or less (see above p. 33) of the 

 coagulable globulins in the earliest stages of the digestion. Albumoses 

 speedily make their appearance, to be somewhat rapidly and it may be 

 largely converted into peptones, of which some are in their turn 

 partially, though never completely, converted into leucin, tyrosin and 

 other less well-defined crystalline products. Similar products of the 

 decomposition of proteids may be obtained by the action of acids alone, 

 in the absence of all enzyme, the preponderance of any one or more of 



1 Vines, Jl. of Physiol. Vol. in. (1880), p. 108. 



2 To this substance the name ' syntonin ' was formerly applied ; this term is 

 however most appropriately used to denote that form of acid-albumin which results 

 from the action of acids on myosin. (See above p. 16.) 



3 Kiihne, Verhand. d. naturhist.-med, Ver. Heidelb. N. F. Bd. i. (1876), S. 236. 

 Schmidt-Miilheim (Arch. f. Physiol. 1880, S. 36) named these antecedents of the 

 true peptones ' propeptone. ' See also Virchow's Arch. Bd. i. (1880), S. 575. 

 Jahresber. d. Thierarzneischule, Hannover, 1879-1880. Biol. Centralb. Bd. i. 

 (1881-2), Sn. 312, 341, 558. 



4 Name due to Lehmann 1850, Physiol. Chem. (Ed. Cav. Soc.) Vol. n. p. 53. 

 Peptones were first definitely described by Mialhe, Jn. de Pharm. et de Chim. 

 (3 Ser.) T. x. 1846, p. 161. 



