POWER OF PANCREATIC JUICE. 71 



imum production, which is 13 or 14 hours after a meal, does not coincide 

 with the period of most energetic digestion. 



With these statements of the nature of the various juices which pass 

 into the small intestine, we may proceed to investigate the phenomena 

 of the digestion carried on in that tube. 



In 1832, Dr. Bright, to whom medicine is so much indebted for his 

 discoveries in relation to the pathology of the kidney, pub- Emulsifvin(r 

 lished three cases of disease of the pancreas, attended by the power of pan- 

 appearance of a large quantity of fat in the faeces, and drew c 

 the inference that in such morbid states the fats are imperfectly digested. 

 More recently, M. Bernard has published experimental evidence to prove 

 that the digestion of the fats consists in bringing them into the condition 

 of an emulsion, and that the pancreatic juice accomplishes this object. 



Whatever influence the pancreatic and enteric juices can exert on 

 starch and oil outside of the body, in artificial experiments, they un- 

 doubtedly exert it in the small intestine as long as the temperature is 

 the same. On starch, the action, as has already been stated, is to effect 

 its conversion into sugar, and then into lactic acid. The oils are turned 

 into emulsions. The constitutional relation between starch and lactic 

 acid is such, that if, in presence of water, one atom of the g ubdiv i s i on O f 

 former be equally and systematically split or divided into starch into lac- 

 two portions, those portions are atoms of lactic acid. And 

 since this substance contains no nitrogen, its oxidation either artificially 

 or in the interior of the system gives origin to carbonic acid and water 

 bodies which can at once b removed by the action of the skin, or the 

 lungs, or the kidneys. 



Respecting the digestion of the carbohydrates cellulose, gum, starch, 

 and the different kinds of sugars, it may be remarked, that eel- Digggfon of 

 lulose, of which the pith of elder is an example, and which the carbohy- 

 occurs in a pure form in Swedish filtering-paper, not only re- 

 sists, in artificial experiments, the action of the digestive juices, but also 

 it would appear to do so naturally in the higher tribes, and hence it is 

 abundantly found in the excrement of the herbivora. To this statement, 

 perhaps, however, the case of the beaver affords an exception, Digestion of 

 there being reason to suppose that this animal possesses the cellulose, 

 power of digesting cellulose. 



There can be no doubt, moreover, that many insects have the same 

 power, for chitin, which may be obtained from their wing-cases, and which 

 retains the appearance of the structure of the part, may be considered as 

 cellulose united with a nitrogenized body, having the constitution of in- 

 sect muscular fibre. This substance not only constitutes the skeleton 

 of insects, their scales, hairs, and enters into the construction of their 

 tracheae, but even forms one of the coats of their intestinal canal. Since 



