35 
structure of the brain and nerves , &c. 
In the skate, the blood globules are of a very large size, 
and have an oval form ; the colouring matter in them is of 
alight yellow; they very readily change their appearance 
when decomposition begins to take place : at this time the oval 
becomes flattened, and the central part appears more dense 
than the margin, by which it is surrounded in the form of a 
ring, and when this ring dissolves, the globule it contained is 
seen of a spherical form, and the surrounding fluid has oil 
floating in it, distinguishable by the naked eye, as well as 
by other tests. 
The globules are represented in PL III. fig. 5. magnified 
4000 diameters. 
The salts in the skate's blood must be very abundant, 
since they are found in it crystallized, as represented in PL 
III. fig. 6 : magnified 200 times. 
On the branch of the vas breve carrying the fluids from the sto- 
mach through the splenic vein to the vena portarum. 
The discovery of valvular vessels in the brain, acting as 
absorbents in that organ, immediately led me to suspect 
that there must be a similar provision for carrying off' the 
fluids taken into the stomach, whenever the quantity or qua- 
lity interfered with the process of digestion. To do this by the 
route of the thoracic duct, was not only too circuitous to cor- 
respond with the general simplicity of the operations of nature, 
but was mixing these heterogeneous liquids in too crude a state, 
with the general circulation of the blood. That there was 
some unusual mode of conveying fluids from the stomach to the 
