390 THE EXCRETIONS: 



The bicarbonate of iron in the water is decomposed at the tem- 

 perature of the stomach, and the iron precipitated either as a 

 protoxide or as a hydrated peroxide, and immediately redis- 

 solved by the free acid of the gastric juice. This reacts on the 

 sulphuret of sodium, and sulphuret of iron is the result. 



Since the publication of Kersten's paper, a very similar view 

 has been propounded by Dr. Bley, namely, that the green eva- 

 cuations observed after the use of calomel are dependent not on 

 the presence of bile, but of sulphuret of mercury. Unfor- 

 tunately for this theory the mercury cannot be detected by ana- 

 lysis, and Pettinkofer's test reveals the presence of bile. 



Dr. Frankl has published a paper containing various argu- 

 ments in opposition to Kersten's views, and criticising his 

 conclusions. 



Berzelius, on the other hand, writes thus : " It never entered 

 my mind to suspect that this coloration arose from sulphuret 

 of iron, but I always believed that it might be attributed to the 

 black oxide of iron. It is, however, quite natural that as sul- 

 phuretted hydrogen is usually produced during the progress of 

 digestion, the oxide of iron present in the intestinal canal should 

 be reduced to a sulphuret, no matter whether sulphates have 

 been given or not." 



Berzelius renders Kersten's view more general, observing 

 " that every chalybeate water, whether it contain sulphates or 

 not, produces a similar appearance in the evacuations." On 

 this Kersten remarks : that " the coloration may be most 

 intense when sulphates are present, because by their decompo- 

 sition during digestion an excess of sulphuretted hydrogen will 

 be generated."] 



Vomitus. (Matters discharged by vomiting.) 



It is well known that the fluid which is found in the stomach, 

 and which is a mixture of gastric juice, saliva, and remnants of 

 food, becomes much changed in its properties in certain morbid 

 conditions of the system. I need scarcely refer to the excess 

 of free acid, and to the presence of bile in certain conditions of 

 the stomach. On the occurrence of the latter of these states 

 we usually observe a separation, or peeling off, of the upper 



