490 REPORTS ON THE STATE OF SCIENCE. 



hydrochloric acid ' is included both the free acid and that combined with 

 proteids and nitrogenous organic bases. Much misconception has arisen 

 in the use of the terms ' free ' and ' combined ' as applied to HCl in the 

 gastric contents ; but inasmuch as the latter may have been ' free ' a short 

 time previous to its estimation, the exclusive determination of 'fi'ee' HCl 

 alone cannot but lead to fallacious conclusions. The method adopted, 

 after careful consideration, for the estimation of the physiologically active 

 HCl is based on Luttke's modification of Volhard's volumetric estimation 

 of chlorides by precipitation with excess of standard silver nitrate solution 

 in the presence of free nitric acid, and subsequent determination of the 

 excess of silver nitrate by standard ammonium thiocyanate, using iron- 

 alum as indicator. 



By estimating (a) the total chlorides and (b) the inorganic chlorides 

 in an aqueous solution of the gastric contents, by this method, the physio- 

 logically active HCl (« — />) is obtained. A further determination (c) of 

 the total acidity with standard sodium hydrate, using phenolphthalein as 

 an indicator, gives, in addition, the free organic acids [c — (« — 6)] in terms 

 of hydrochloric acid. 



It did not, at first, seem feasible to determine these constituents of 



the ga.stric contents in single stomaclis, owing to their small weight 



(frequently not exceeding 05 gramme), and therefore estimations were 



made, in the earlier experiments, on batches of stomachs varying in 



number from six to sixty. 



. N N . . N . 



Later, by using ^ or :^ standard solutions in place of - solutions 



and slightly varying the details of the method, it proved possible to 

 make the estimations, with accuracy and comparative ease, with single 

 stomachs. 



In the first five series of experiments no account was taken of the 

 period of digestion, the mice being simply removed from their cages 

 while feeding. Under these conditions the results obtained somewhat 

 unexpectedly indicated an increase in the .secretion of physiologically 

 active HCl in mice with transplanted tumours as compared with normal 

 mice, the average amounts of HCl being 0'17r)2 per cent, and 0'1121 per 

 cent, on 178 mice and 150 mice respectively. 



Next, a numl)er of experiments were made to determine, if possible, 

 the usual period of digestion for normal mice ; but the results obtained 

 after periods of half an hour, one hour, and one hour and a half respec- 

 tively showed that while, on the whole, more mice attained a maximum 

 secretion of HCl in one and a half hours, many attained a maximum at 

 one hour, and some even at lialf an hour. Parallel experiments were 

 made with mice with transplanted tuinours for the same period of diges- 

 tion. Similar variations were found, for these periods, to those observed 

 in normal mice, but with a general tendency to increase of HCl. 



Summarising the results obtained in the experiments relating to 

 definite periods of digestion, the examination of 245 stomachs from 

 normal mice gave an average of 01456 per cent. ; and of 290 stomachs 

 from mice with transplanted tumours, 0'1G73 per cent., for periods of one 

 hour's digestion. 



Thirteen single rat stomachs, weighing with contents from 2'5 to 

 10 grammes, were also examined. Six of the.se were from normal rats 

 and seven from rats with transplanted tumours, the tumours varying in 

 weight from 0-3 to 15 grammes. The former gave an average of 0-1427 



