1884. ] Microscopy and Histology. 327 
carminic acid, took a fine coloration of mercuric carminate. So, 
too, specimens colored in alcoholic carminic acid can be changed 
by a few moments’ treatment with a very dilute alcoholic solu- 
tion of lead-acetate or cobalt nitrate to a beautiful purple. With 
lead acetate used as abovea double coloration is sometimes pro- 
duced, but I have not examined sufficiently these colorations to 
accurately describe them. Cupric and other salts, used as above 
described, have not given me very favorable results. Sometimes 
salts in the tissues of the animals themselves change portions of 
the carminic acid to purple carminates, giving a double coloration 
without further treatment. 
Picric acid added to alcoholic carminic acid in extremely small 
quantities (best in a dilute alcoholic solution, testing the solution 
on specimens after each addition) makes a double alcoholic color- 
ing fluid (a so-called picro-carmin). I have been unable thus far 
to determine the proportion of picric acid required for this solu- 
tion, having in every case added an excess. All different kinds of 
carmin solutions can be made from carminic acid with the ad- 
vantage of having always uniform strength, of being definite 
mixtures, and of not spoiling as readily as those made directly 
m cochineal, 
Incompatible reagents with carminic acid are, of course, all 
aline solutions and nearly all metallic salts; with ammonic 
carminate, are naturally all acids ; with all carmine solutions, are 
mine and chlorine. 
I hope later to try some coloring experiments with coccinin, 
tuficoccin, carmin red, and ruficarmin, all of which are derived 
m carminic acid, and of possible value to the histologist. 
CTURE OF SECRETORY CELLS AND THEIR CHANGES IN 
SECRETION —The histological structures of the various secretory 
cells have been described by different observers, as well as the 
changes undergone in them during the act of secretion. But 
re descriptions exhibit many discrepancies, which are largely 
a to the differences between the methods employed in study- 
aaa aues. Mr. J. N. Langley, whose experience eminently 
glands ur conceptions of the secretory cell. He says: “The 
f vertebrates in which I find that the secretory cells have 
Saliva 
of ty glands, and the similar glands of the mucous membrane 
ions, the ‘chief’ cells of mammalian gastric glands; the 
have c glands of such birds, fishes, reptiles and amphibia as I 
Creas - ined; the cesophageal glands of the frog; the pan- 
vr S Ri ke o S 
ornate : The cell substance is composed of (a) a 
