268 LECTURE XII. 



that it is impossible to give a perfectly clear picture of the metabolic 

 disturbance in question, which shall be based upon our present experi- 

 mental knowledge. If we base our judgment concerning this anomaly in 

 albumin-metabolism not only upon the observations made upon those 

 afflicted with cystinuria, but upon our general knowledge of the total 

 metabolism of albumin in the tissues, it then appears as most probable 

 that we have in cystinuria a disturbance in the decomposition of proteins 

 in the cell-metabolism. Conversely, we can consider the appearance of 

 cystine in this disease as further evidence of the formation of amino acids 

 from albumin in the intermediate metabolism, always remembering that 

 one supposition is dependent on the other, and thus it is not a definitive 

 proof. 



Our insight into the intermediate decomposition of albuminous bodies 

 is by no means limited to the discovery of amino acids in the urine 

 under specific conditions, and to the recognition of the final albumin 

 cleavage-products, urea, in the case of mammals, and uric acid in birds 

 and fishes. There are other products present in the urine, as yet largely 

 unknown, which contain nitrogen and sulphur, and are undoubtedly 

 closely related to albumin-metabolism. We will disregard the fact that 

 there are albuminous substances in urine which have been variously inter- 

 preted. They are probably not simple substances. They belong partly 

 to the mucins, and in part to the group of nucleo-albumins, and probably 

 originate in the urinary passages. They have no bearing on the subject 

 of albumin-metabolism. This applies especially to the large quantities 

 of albumin which appear in the urine under pathological conditions, and 

 especially in diseases of the kidneys. These only affect the albumin- 

 metabolism indirectly, inasmuch as they continually withdraw this valuable 

 material from the body, thus depriving the organism of the energy con- 

 tained therein. It is indeed possible, that an exact examination of these 

 substances would give us an insight into the course of albumin decompo- 

 sition in the tissues. It would certainly be of the greatest interest to 

 know the origin of the albumin always present in the various forms of 

 nephritis. 1 We usually assume that the serum-proteins (serum-globulin, 

 and serum-albumin) under pathological conditions pass into the urine. 

 Although this assumption is very plausible, it must be said it does not 

 necessarily explain all the cases arising. That albumin does not normally 

 appear in urine, excepting, of course, in traces, is due to the fact that the 

 epithelial cells of the kidney, or those of the glomeruli, will not permit the 

 colloidal albumin to pass through. This simple explanation is not inva- 

 riably true, as is shown by the appearance of a very well-defined albumi- 

 nous substance, the so-called " Bence- Jones albumin," in the urine. It is 



1 E. Abderhalden: Z. exper. Path. u. Therapie, 2, 642 (1905). 



