249 
It is worthy of remark that this experiment amply demon- 
strates the inestimable advantages of high objectives (which 
some even yet pretend to doubt), for the remarkable move- 
ment of the contained molecules seems to have escaped the 
attention of Prof. Virchow, the great author of f The Cellular 
Pathology,’ himself (vide p. 181, Chance’s translation, 1863). 
Although the observation was first made with the aid of a 
-jL-th, yet afterwards, knowing exactly what to look for, I had 
little difficulty in demonstrating to various gentlemen the 
revolving molecules thus brought into view with powers as 
low as the -ith inch. 
A portion of fetid pus from an abscess, and a specimen of 
mucus from the nasal fossa, under a like treatment, gave 
similar results, which did not materially vary in numerous 
trials. 
Tracing now the white blood-corpuscle from its condition 
of irregular outline and amcebaform movement, as observed 
in serum and in heavy urine, when the circumambient fluid 
approaches the density of 1028, through its rounded form 
M'ith slightly more distinct nuclei, in the liquor puris, and in 
urine of lower specific gravity, we find that immersed in a 
rarer liquid, approximating to the mean density of the saliva 
(1005), it has an accurately spherical outline, is more than 
twice the magnitude, and contains a number of minute 
actively moving molecules, thus exactly resembling in all 
sensible characters the true salivary corpuscle ; and it there- 
fore seems reasonably certain that the blood, under the 
appointed nervous influence, congesting the buccal mucous 
membrane and associated glands, moves slowly enough 
through their capillaries to allow some of its white globules 
to penetrate the walls of the vessels, as they are said to do 
those of the frog’s mesentery in Cohnheim’s experiment 
(Virchow, ‘Archiv,’ Band 40, S. 38, u. s. w.), which, under 
the influence of the rarer saliva, expanding them and setting 
free to move their contained molecules, constitute the bodies 
so long known to histologists as the corpuscles of the salivary 
fluid. 
Dr. Lionel Beale, in his work on the ‘ Microscope in Prac- 
tical Medicine,’ remarks in reference to the examination of 
the saliva — “ In the somewhat viscid matter of which the 
salivary corpuscle is composed, are multitudes of highly 
refracting particles in incessant motion. The nature of these 
particles is extremely doubtful. They look very like the 
germs of bacteria, and it is possible they may be of this 
nature.” If the hypothesis thus guardedly indorsed by the 
celebrated English microscopist be correct, it seems not im- 
