SCIENTIFIC SUMMARY. 
209 
PHYSIOLOGY. 
The Phenomena of Digestion in the Stomach. — M. 0. Richet has had an 
opportunity of renewing the direct observations made in America many 
years ago by Dr. Beaumont upon the action of the stomach. A boy, suffer- 
ing from an impassable constriction of the oesophagus, was operated upon by 
Professor Verneuil, who performed upon him the dangerous operation of 
gastrotomy. The operation was successful, and established a permanent 
opening into the stomach, through a sound placed in which the necessary 
food was administered to the patient. In some respects the case was par- 
ticularly important, as the complete impermeability of the oesophagus pre- 
vented any admixture of saliva with the gastric juices. M. Richet found 
that the stay of the food in the stomach was rather variable, but it was 
generally from three to four hours in the case of ordinary food, such as 
starchy materials, fats, and meat. With milk the stomachal digestion 
lasted from an hour and a half to two hours ; the absorption of water and 
alcohol was much more rapid, as no traces of them were to be found in from 
thirty-five to forty-five minutes. The food does not gradually disappear 
from the stomach, but apparently it passes through the pylorus almost, as 
the author says, en bloc. During the first three hours of digestion the 
volume of the mass of food is unchanged; then, within a quarter of an hour 
at the utmost, the whole has passed away. Hunger is not caused simply by 
emptiness of the stomach ; the organ is generally empty in four hours after 
a meal, but the sense of hunger is not felt until the lapse of about six 
hours. 
To obtain pure gastric juice, M. Richet first washed out the stomach 
several times with distilled water, and then gave the unfortunate boy some- 
thing tasty to chew, when by a reflex action the secretion of gastric juice 
was pretty abundantly produced. The average acidity of the gastric juice, 
whether pure or mixed with food, was found to be equivalent to T7 grains 
of hydrochloric acid per 1,000 grammes of liquid. It varied from 0-5 to 
3*2 grains. Wine and alcohol increase the acidity ; cane sugar diminishes 
it. When acid or alkaline liquids are injected into the stomach its fluids 
tend rapidly to resume their normal acidity, the latter being attained in 
about an hour. The gastric juice is more acid while digestion is going on, 
and the acidity increases slightly towards the end of the operation. — 
Comptes rendus de V Acad, des Sci., March 5, 1877. 
ZOOLOGY. 
Protective Mimicry in Pats. — Dr. Archer has noticed that a Brazilian 
bat ( Rhynchonycteris naso ) presents an example of protective mimicry, 
inasmuch as, during repose, it hangs from the branches of trees with its 
wings extended, so as easily to escape notice among the leaves. Dr. Dobson, 
in a letter to “ Nature ” (February 22), in reply to that of Dr. Archer, indi- 
cates other instances of mimicry in the same order of mammals. Thus 
Kerivoula picta, Vespertilio formosus and V. Welwitschii, although differing 
in several respects, and inhabiting widely separated regions, exhibit a 
