PEPSINE. 
339 
In order to reduce it to powder, M. Boudault simply eva- 
porates his artificial gastric juice to a syrupy consistence, 
and to this he adds dried starch in such proportion that one 
gramme (15 grains) shall be in a position to digest four 
grammes of dry fibrine, when the two are submitted to- 
gether in the presence of water to the temperature of the 
human body. 
The substance thus produced is a fawn-coloured powder, 
cohering somewhat together, and possessing a peculiar taste 
and odour. It yields to water, the lactic acid, and the pep- 
sine, producing a solution of a yellowish tint, with the colour, 
odour, and taste of gastric juice. 
A solution of pepsine, that is to say, the neutral artificial 
gastric juice, presents the following reactions Salts of lead 
and mercury give rise to precipitates, which, when decom- 
posed by sulphuretted hydrogen, reproduce the pepsine with 
its physiological properties. Tannin likewise precipitates 
pepsine, but the precipitate has no power whatever of 
digesting fibrine. Rectified spirit precipitates the pepsine 
from its solution. This precipitate is soluble in water. Ab- 
solute alcohol dehydrates pepsine, and destroys, or at all 
events greatly diminishes its digestive power. One property, 
however, which pepsine possesses, which is very charac- 
teristic, and which is a fruitful source of failure in its pre- 
paration, is, that at the temperature of about 120° Fah., its 
solution becomes slightly turbid, and loses entirely its digestive 
properties. 
There has been considerable difference of opinion with 
regard to the nature of the acid in the natural gastric juice ; 
some chemists assert, that the acidity is mainly due to 
hydrochloric acid, some are advocates for phosphoric acid, 
others again for lactic acid, but it is universally admitted 
that the gastric juice must be acid, to produce its physio- 
logical effects, and that lactic acid is always present to a 
greater or less extent. Lehmann found, that w T hen gastric 
juice is distilled, the first portions w’hich passed over w-ere 
free from hydrochloric acid, but as the liquid became more 
concentrated, hydrochloric acid was obtained ; and this he 
ascribed to the property possessed by concentrated lactic 
acid of decomposing the compounds of the strongest acids, 
and in this case to the decomposition of the chloride of 
sodium. 
In order to determine this question, M. Boudault made 
the following experiments. He first wished to ascertain 
whether the gastric juice, as it issued from the mucous 
membrane, was acid or not. With this view, the rennet-bags 
