METAMORPHOSIS OF TISSUE. 



instance, in the crystalline lens of the eye, as was observed by 

 Wohler, and in the sweat, according to the investigations of 

 Schottin and Favre. Liebig's conjectures may therefore be per- 

 fectly correct, that the absence of urea as well as of common salt 

 in the muscular juice, and the passage of urea into the circulation, 

 and its excretion by the kidneys, have a close relation with the 

 presence of chloride of sodium in the blood. 



Liebig observes, in relation to the combination of grape-sugar 

 with chloride of sodium, that we are instinctively led to add salt 

 to amylaceous food (which during. digestion yields much sugar) in 

 far larger proportion than to other food. The saliva and the 

 pancreatic juice, which more especially conduce towards the con- 

 version of starch into grape-sugar, contain a preponderating 

 quantity of chloride of sodium in their solid constituents. 



Diabetic urine always contains, in addition to free grape-sugar, 

 the compound of this sugar with common salt, and it frequently 

 happens that this is the only compound which separates in crystals 

 from diabetic urine. It is not, therefore, an irrelevant question to 

 inquire, on the one hand, into the relation of the chloride of sodium 

 to grape-sugar in the digestion of amylaceous substances, and, on 

 the other, into its separation through the kidneys in diabetes. 



Slightly based as the assumptions may be, which can be 

 deduced from the chemical affinities of chloride of sodium in 

 reference to the purposes which this substance accomplishes in the 

 animal organism, there are some facts which can only be explained 

 by a decomposition of this salt in the animal body, and which may 

 therefore throw additional light on its utility in the animal 

 economy. The most striking of these facts is the occurrence of 

 free hydrochloric acid in the gastric juice ; at all events, it appears 

 from the most recent investigations of C. Schmidt that free hydro- 

 chloric acid may be present in this secretion, without lactic acid 

 or lactates. It certainly remains a mystery for the present how 

 this decomposition of the chloride of sodium is effected. Another 

 less obvious, but not the less remarkable fact is, that even in the 

 blood of herbivorous animals., which take up almost solely potash 

 salts in their food, there are in every 4 parts of alkaline carbonate 

 in the blood-serum at least 3 parts of carbonate of soda, and only 

 1 part of carbonate of potash, whilst in the muscular juice of 

 carnivorous as well as that of herbivorous animals chloride 

 of potassium is almost solely found. This fact, which was dis- 

 covered and mainly established by Liebig, shows, on the one hand, 

 that the chloride of sodium in the blood must necessarily undergo 



