relation existing between these and urea in the normal metabolism of tissue. The physiological action of lysatin has not been as yet studied, nor is it known whether or not it would reappear in the urine as urea if given by the mouth or intravenously. We may sum up the positive knowledge which we have on this point as follows: I. A number of substances belonging to the kreatin group are formed from proteids (some in the body, as kreatin, kreatinin, kruso-kreatinin, xantho-kreatinin and amphi-kreatin, and some by artificial means, as lysatin and lysatinin); 2. Kreatin is a substituted guanidin; 3. Methyl-guanidin is a highly poisonous substance, and this is true of both that obtained from putrefying flesh and that prepared from kreatin. It produces marked dyspnoa, muscular tremor and general clonic convulsions. That there is a marked disturbance of tissue metabolism caused by the inhalation of vitiated air has been shown by Araki.1 In the urine of animals rendered unconscious by being kept in a confined space this experimenter found albumin, sugar and lactic acid. If the animals had been kept without food for some days before being subjected to this experiment, albumin and lactic acid, were found, but no sugar appeared. This was undoubtedly due to the fact that the glycogen of the body had been exhausted by the fasting. Identical results were observed in animals, which were poisoned with carbon mon-oxide. Dogs which were poisoned with curare, and in which the respiratory movements were maintained artificially secreted very little urine, but the blood was found to contain considerable quantities of sugar and lactic acid. The urine of frogs in which the respiration was retarded by the production of tetanus with strychnia secreted urine containing sugar and lactic acid. In the urine of three epileptics there were found albumin and lactic acid directly after the seizure. The factor common to all these cases is diminished oxygenation of the blood, and to this is ascribed the appearance of the abnormal constituents of the urine. These investigations demonstrate the influence of impure air upon the chemistry of the living cells of the animal body. The chemistry of the absorption of foods offers an interesting chapter in the study of the activity of the animal cell. As practitioners of medicine we bestow much attention upon the subject of digestion. We administer acids and digestive ferments, often without effect. The manufacturing chemists flood the market with preparations of pepsin and pancreatin, with their so called malted and digested foods, and I fear that we too often are deluded with the idea that it is only necessary to supply our patients. with these ferments or foods in order to build up a worn-out body and restore strength to weak muscles and exhausted nerves. There is a popular-I fear that I might without any exaggeration say a professional-idea that peptones filter through the walls of the intestines without let or hinderance, and pour their treasures of strength and energy into the blood-vessels. However, scientific experiments have shown that this is altogether erroneous. In the first place albumin may be absorbed without having been previously converted into peptone. Voit and Bauer1 washed out loops of the small intestines in living dogs and cats, ligated both ends of the loop, injected into the loop albuminous solutions, replaced the intestine within the body, and after from one to four hours determined the amount of albumin remaining in the loop. It was found that the amount absorbed during this time was, for egg-albumin from 16 to 33 per cent., and for acid albumin from muscles, from 28 to 95 per cent. Voit and Bauer think that they proved that there was no active digestive ferment in these loops by demonstrating that the portion unabsorbed contained no peptone, The experiments of Eichhorst have led him to the same conclusion, but the most positive evidence which we have on this point has been furnished by the investigations of Czerny and Latschenberger." In a case of preternatural anus at the sigmoid flexure, it was found that albuminous solutions injected into the thoroughly washed piece of intestine below the fistula were absorbed after from twenty-three to twenty-nine hours to the extent of from 60 to 70 per cent. Without citing further experimental evidence upon this point it is sufficient to say that it has been conclusively shown that albumins may be, and often are, absorbed to a marked extent, without previous conversion into peptone. It should be understood that I do not claim that eggalbumin is ordinarily absorbed unchanged, but as Prior1 has shown even this may occur when excessively large amounts of egg-albumin are taken in the food. (In such a case the albumin is not apparently utilized by the tissue, but acting as a foreign body, it is eliminated in the urine.) But there are many reasons for believing that in health a small part of our proteid food is never converted into peptones, but is fitted for its service to the animal economy during its absorption through the walls of the intestines. The active agents which render this portion fit to enter the circulating blood are not the unorganized, digestive ferments, but are the living cells of the absorbing mechanism, There are some good arguments in favor of the theory that all the proteid which is utilized in building or repairing tissue escapes conversion into peptones in the alimentary canal, and that proteids which have been converted into peptone can serve only as a source of energy, but cannot be utilized by the animal cell in the reconstruction of wasted muscles. If the defibrinated blood of one dog be injected directly into the veins of another the amount of urea eliminated by the latter is not materially increased, but if the defibrinated blood be administered by the stomach the increased amount of urea is large and in exact proportion to the quantity of the proteids in the blood administered. A still more important fact is the demonstration that peptone is converted into serum-albumin during absorption. Should the peptones reach the circulation unchanged they act as poisonous bodies. Injected into the blood they are soon eliminated unless the quantity is sufficiently large to cause marked toxical effects. The conversion of peptone into albumin by the mucosa of the walls of the alimentery canal has been beautifully shown by Salvioli working under the direction of the veteran physiologist, Ludwig. A loop of the intestine with the attached messentery was taken from a dog. In the piece of the intestine there was placed one gram of dissolved peptone. Then the collateral branches having been ligated, a stream of defibrinated blood diluted with salt solution was caused to flow for four hours through the attached branch of the mesenteric artery. Duriug this time the fact that the cells of the intestine retained their vitality was shown by the active contractions of the piece. At the expiration of the given time there was no peptone either in the intestine or in the blood. A further experiment showed that peptone added to the injected blood did not disappear. Consequently the only conclusion which is warranted by the facts is that the peptone is converted into albumin during its passage from the lumen of the intestine into the blood. That the living cells of the mucous membrane |