161 
The colourless corpuscles are spherical in shape, and vary in 
diameter from the 3450th to the 2100th of an inch; the majority 
however measure about the 3000th of an inch. Their structure is 
granular, and in about the same degree as the colourless corpuscles 
of blood, and the ordinary exudation corpuscles, to which they pre- 
sent a strong resemblance. 
Many of these bodies preserve their figure for a considerable time, 
while others become collected into clusters and form irregular broken 
masses. 
The coloured corpuscles are irregular in size and shape, and are 
eomposed of an aggregation of minute elongated and sometimes 
triradiate bodies, many of which appear, from their irregular and 
obscure outline, as though partially dissolved. In the immediate 
neighbourhood of these, the fluid has a much deeper colour than 
elsewhere. From these circumstances I have been led to conclude 
that the general pink colour of the fluid is due to the solution of the 
coloured particles, and not simply to their presence. In this parti- 
cular the fluid under consideration is strikingly different from blood, 
which owes its colour to the presence of coloured globules and not to 
their solution. 
The colourless corpuscles are represented in the figure at A, and 
the coloured ones at B, together with the deeper colour of the fluid at 
the part in which the latter are present. 
These observations were made May 28th, 1850. Since that time 
I have on several occasions sought to obtain a little more of the red 
exudation, but always without success. The creature on leaving the 
bath feels slimy, and a small quantity of transparent tenacious fluid 
issues from the elevations on the skin, but it quickly dries up. 
On Sunday last, June 23, the nose was covered with colourless 
exudation, and near the upper margin of the nostril it had a percep- 
tible pink tinge. On this occasion the animal had been out of the 
bath for some hours, and the skin of the body was perfectly dry. 
Whether the red colour of the exudation is a condition of youth, 
and of an imperfect condition of the skin, and has ceased im con- 
sequence of the increased age of the animal and the consequent more 
perfect development of the integument, or has ceased in consequence 
of the change of climate to which the animal has been lately subjected, 
is a question which, with the facts at present at our disposal, can- 
not be satisfactorily determined. 
We have however sufficient evidence to warrant the conclusion, that 
the thick tenacious exudation, whether coloured or otherwise, is 
poured out only during the time the skin is immersed in water, and 
that it has an especial reference to the aquatic habits of the animal. 
It appears for the time to convert the surface of the body into a mu- 
cous membrane, and then, on the animal leaving the water, to furnish 
by its inspissation an epidermis. ; 
Should further inquiry show that the thickness of the exudation 
arises from a solution of the colourless globules, its relation to mucus 
will be still further established, and a microscopic examination into 
No. CCXI.—Procrepines or tHE Zoouocicar Socrery. 
