418 COLLECTED STUDIES IN IMMUNITY 



Besides this, however, one could assume that analogous dyes also 

 effect a loose combination with the blood albumin, which makes 

 excretion through the kidney impossible. In that case the condi- 

 tions would be analogous to those which we see with many metals, 

 e.g. iron or lead, and to those which obtain in the excretion of a 

 poisonous albuminous substance, ricin, as they have been deter- 

 mined by investigations in the Pasteur Institute. None of the sub- 

 stances which occur in the circulation in the form of albumin com- 

 binations pass into the urine, since the albumin molecule is unable 

 to pass through the intact kidney filter. In contrast to this, how- 

 ever, the intestinal glands or liver allow even these large-moleculed 

 substances to pass through. 



The salivary glands do not play any important part in elimina- 

 tion, as is shown by the fact that with the majority of dyes the saliva 

 is not at all colored, and with certain others, e.g. alizarin blue, is 

 but slightly tinged. This is apparently because of the fact that the 

 salivary glands are not well adapted to the secretion of substances 

 with large molecular weights. In the excretion of substances of 

 small molecular weights, however, they may play a prominent role, 

 as can be seen from the behavior of various salts, e.g., potassium 

 iodide, rodan combinations, and the salts of mercury. In the aro- 

 matic series it is particularly paraphenylendiamin, dimethylpara- 

 phenylendiamin, trihydroparaoxychinolin , and related substances, 

 which are excreted through the submaxillary gland of rabbits and 

 there give rise to marked inflammatory changes (oedema, necrosis). 



The least important role is that taken by the sweat glands. So 

 far as I am aware the only dyes excreted on the body surface are 

 those of the phosphin series, as is shown by Mannabeig's researches 

 concerning the therapeutics of malaria. 



Much greater significance, however, attaches to the possibility of 

 exactly determining the distribution of the dyes by means of the 

 microscope. I need only call to mind the vital staining of nerve 

 endings by means of methylene blue, a procedure which has found 



are here dealing with large-moleculed substances which are soluble with diffi- 

 culty and which therefore must be regarded more like colloids In contrast 

 to methylene blue, methyl violet, and many other dyes, benzopurpurin is ab- 

 solutely non-diffusible. According to the researches of Krafft (Bericht der 

 deutsch. chem.^Gesell. 1899) solutions of benzopurpurin (raising of the boiling- 

 point) showed an apparent molecular weight of 3000 instead of 774 reckoned 

 out from the formula. 



