16 BULLETIN OF THE BUREAU OF FISHERIES. 
Acidity of the gastric juice.—Richet (1878) found the acidity of the gastric juice 
of fish to be much greater than that of mammals. Thus he found the acidity of fish 
he studied to be as follows: 
a : 
meer | Parts in | 
ESE | 1,000. 
Skate!(Rajai clavate iia) oss tosotecee nee. eee eee 
| Op Hivs piscaLOTiuseee ee ee nee eee ee een eee 6:2) | 
Squalus squatina ............... ee eteeee| 6.9 | 
Scyllitimi cali See eee eee eee | 6.9 
|| ‘Seylilitumicaniculas sss.) ose eetee see eee eee eee 14.9 
RRS Udcineeempseacssaucde nootr asoAG. baogonserassanocs. 6.0 | 
The acidity Richet found to be due to an acid not soluble in ether. He believed 
that the acid was hydrochlorie acid combined with some organic substance, as leucin 
or tyrosin. 
Yung (1899) in his study of the gastric juice of Sceylliwm canicula found the 
mean of four analyses to be 0.84 per cent. 
The acidity of the stomach of elasmobranchs is greatest when the fish is in full 
digestion. Indeed, the fasting stomach is practically neutral. In order to study 
the acid, phenolphthalein, alizarin, and dimethyl-amido-azobenzol were used as 
indicators as recommended by Webster and Koch (1903) in their Laboratory Manual 
of Physiological Chemistry (p. 36), and experiments were made to determine: 
(a) The total acidity of the stomach content in terms of hydrochloric acid; (b) the 
physiologically active hydrochloric acid; (c) the free hydrochloric acid. The results 
are given in the following table: 
Physiologically | Highest 
Total acidity in active hydro- | percentage 
Species. percentage hy- ehloric acid, | free hydro- 
droehloric acid, average per- ehloric 
centage. acid, 
{0-04-1.00. : 
Miustelus (Camist....2.ses228 i$. aciieccts seals S408 Fore Sie SRE Braue |, Average, 0.738. 0.538. 0.2. 
|50 individuals. 6 individuals. 
0.1-1.2. 
Carchariaswiitoralisiass seme eee aa Bo re oSOnScas= -|; Average. 0.87. 0.614. 0.381. 
||25 individuals. 10 individuals. 
aC = bE cae \fAverage, 0.67. No tests. No tests. 
Squalus acanthiasy.— 2% ss sk oe fossa sc ter sae es Leen ee = ee ee 160 individuals. 
f x see a : jAverage, 0.55. 0.493. 0.254. 
Carcharhinus'ObSCunus ss. essences oe ee ce araaee eee eee ce eee eee \2 individuals, 2 individuals. 
; aA (0.275. 0.229. 0.172. 
STA UC OTE Ce ee \1 individual. 1 individual. 
xe ae see s 0.93. 0.812. | None. 
Galeocerdo tigrinus -.-.-.-------------+-020-2222 02220202 ce ee eee eee \1 individual. 1 individual. 
0.51 No tests. None. 
Tetronarce OCcidentalis= ss req sma siesta ete aise eet ia eee eee eet 
fO.51. 
{U individual. 
In the case of Carcharias littoralis and Carcharhinus obscurus the physiologically 
active hydrochloric acid was determined as follows: (a) By neutralizing 10 ¢.c. of the 
stomach contents, evaporating, calcining, and finding the total chlorides by titrating 
with normal silver nitrate; (b) by evaporating, calcining, and finding, by titrating 
with the silver nitrate solution, the chlorides in a nonneutralized 10 ¢.c. of the 
stomach content; (c) subtracting (b) from (a). The results were as follows: 
Total acidity in terms of hydrochloric acid (phenolphthalein indicator): 
Per cent, 
@archarids littoralisi<.. =; 222-22 oe ee eee ea: 
