216 
to accept them simply as useful measures for the capacity of 
the higher objectives, and passed on without any attempts to 
solve the mystery of their origin ; Kolliker, indeed, advanced 
the theory that they were essentially a form of exudation- 
corpuscles, but hitherto his hypothesis does not appear to 
have been generally accepted by microscopists as a fixed 
fact. 
The following experiments, undertaken to elucidate their 
constitution, were performed with the large Powell and 
Lealand’s instrument, so long a denizen of the “ Microscope 
Room ” in the Pennsylvania Hospital, and no doubt endeared 
by constant association to many generations of “ Residents,” 
as well as to myself. When it was discarded by the institu- 
tion I became the purchaser, and after undergoing some re- 
pairs, and having adapted to it a -^til-inch objective (made 
by Mr. William Wales, of Fort Lee, N. J.), it has accom- 
plished the work below described. 
The salivary corpuscles examined under a power of eleven 
hundred diameters present the appearance of perfect sjrheres, 
varying from the —4*0-0 th. to the -ft-T-o ^-th of an inch in diameter, 
each having a very transparent but beautifully defined cell- 
wall of exceeding tenuity, which incloses from one to four 
almost equally transparent nuclei of a circular or oval form, 
whose diameters range from j-oVcrtb to ■roVo th of an inch. 
These nuclei are situated sometimes centrally, but more com- 
monly near one side of the corpuscle, and the cavity between 
the margin and the cell-wall is generally filled with from 25 to 
50 molecules, not more than -^ 0 0 u~ o th of an inch in diameter, 
whose characteristic is that of constant and rapid motion. 
Some of these molecules seem to be elongated into an oval or 
hour-glass form, hut the activity of their movements renders 
it difficult to ascertain this with precision. In my observa- 
tions these corpuscles have appeared to enlarge and become 
flattened, from the pressure of the glass cover, as the stratum 
of liquid beneath became thinner from marginal desiccation, 
so that usually in the course of an hour or so they burst, and 
discharge about one fourth of their contents, when two, three, 
or more of the molecules swim away, continuing their revolv- 
ing movements until they pass out of view ; the other granules 
outside and those remaining within the cell become within a 
very few seconds entirely stationary. If a solution of aniline 
red, of the strength of one grain to the ounce of distilled 
water, be allowed to penetrate at the margin of the cover, the 
nuclei of the salivary corpuscle are readily stained of a bright 
crimson, and are thus exhibited with beautiful distinctness ; 
the dye appears, however, to exert an immediate influence 
