168 ANTISEPTIC ACTION OF GASTRIC JUICE. [BOOK II. 



found in the fact that in a whole series of the lower animals the com- 

 mencement of the alimentary canal secretes a fluid very rich in mineral 

 acid, but containing no ferment and having no special action on the 

 food 1 ." In illustration of his view, Bunge refers to the remarkable obser- 

 vations first made by Troschel and Boedeker 2 , which were afterwards 

 fully confirmed by de Luca and Panceri 3 on the acid secretion of Dolium 

 galea, which will be referred to in detail in a subsequent section of the 

 present volume. It appears to the Author that whilst the value of the 

 germicidal and antiseptic action of the gastric juice rests upon well-ascer- 

 tained facts and cannot be gainsaid, yet the estimate formed by Professor 

 Bunge as to the preponderating importance of this function, compared 

 with the proteolytic action of the gastric juice, is an exaggerated one. 

 The acid secretion in Dolium and other invertebrates is related to the ex- 

 ternal requirements of the creature, and not to its digestive acts ; it enables 

 it, in its search for abode and protection to erode the chalky formations 

 which surround it, and we may assume, perhaps, that it also furnishes it 

 with a chemical agent of offence and defence. May we not in the acid 

 secretion of Dolium see an analogy to the venomous secretions which cha- 

 racterise so many vertebrate and invertebrate animals ? If indeed we 

 determine to establish our opinion as to the relative importance of the 

 various functions of the alimentary canal on the basis of comparative 

 physiology, we shall be forced to a conclusion very different from that of 

 Professor Bunge. The characteristic digestive process in invertebrata is, 

 as we shall see, one which proceeds in alkaline and not acid media, and 

 which bears most resemblance to the pancreatic digestion of vertebrates. 



. tic A series of interesting researches has been carried 



action of gas- 11 ^ i n which the antiseptic action of the gastric juice 

 trie juice in- is indirectly estimated, under various conditions, by a 

 fluences the study of the urinary constituents. 



of iuSe When discussing the putrefactive changes which 

 occur in the intestinal canal, it will be pointed out 

 that, as a result of the action of putrefactive bacteria, there are 

 formed certain phenols, of which the chief are phenol and cresol, and 

 particularly two well-characterised bodies of foul odour, indol and 

 skatol. 



The bodies which have been named are in part excreted in the 

 faeces, but in part are absorbed, and entering the blood are excreted 

 as constituents of the urine, in the form of so-called ethereal sul- 

 phates. Thus phenol, C 6 H 5 . OH, is principally excreted as phenol- 

 sulphuric acid, C 6 H 5 . OSO 2 OH : cresol (methyl-phenol) as cresol- 



sulphuric acid, ^ ~ 



1 Bunge, Physiological and Pathological Chemistry. English translation. Vol. i. 

 p. 158. 



2 Troschel, Poggendorff's Annalen, Vol. xcm. (1854), p. 614, and Journ. f. prakt. 

 Chemie, Vol. LXIII. (1854), p. 170. 



3 de Luca et Panceri, Comptes Eendus, Vol. LXV. (1887), pp. 577 and 712. An ab- 

 stract of these researches, written by the Author, appeared in the first volume of the 

 Journal of Anatomy and Physiology. 



