PRACTICAL DIRECTIONS. 461 
inject the fluid. This will pass into the spaces in the connective 
tissue of the pad, which will swell up, and the colored fluid will pass 
from the connective-tissue spaces into the lymphatics. Pressure must 
be maintained with the syringe for a considerable time,—fifteen 
minutes to a half-hour for a good injection of the main trunks of the 
lymphatics of the limbs. The movement of the fluid should be 
facilitated by pressing and manipulating the limb at the same time 
with the hand,—in such a way as will tend to drive the fluid 
proximad, 
The lymphatics of the head may be injected in a similar manner, 
the canula being introduced into the upper and lower lip, or into 
the bare surface at the end of the nose. 
The internal lymphatic vessels may be injected by injecting the 
lymphatic glands with which they are connected. This may con- 
veniently be done as follows: Draw out to a fine point the tip of an 
ordinary pipette or medicine-dropper. The point should be fine, 
but should taper rapidly in a conical fashion, so that when the point 
is inserted the part of the glass tube behind it will close up the 
opening. 
Fill the pipette with soluble Prussian blue; insert the point into 
the gland, and inject the fluid slowly. The lymphatic vessels passing 
from the glands will be filled. By injecting thus the large lymphatic 
gland (‘‘ pancreas Aselli’’) in the mesentery, the abdominal lym- 
phatics, the receptaculum chyli, and the thoracic duct may be 
injected. 
By using thin gelatine colored with Prussian blue as an injecting 
fluid permanent preparations may be obtained; of course the 
process of injection is then less simple, and should be looked up in 
some manual of methods. 
NERVOUS SYSTEM. 
I. Tue Sprnat Corp (p. 335). 
Use the specimen on which the muscles were dissected. (Or if 
the peripheral nerves are not to be dissected on the specimen used 
for the blood-vessels, that may be employed.) 
Make a longitudinal dorsal median incision of the skin, between 
the back of the head and root of the tail. Reflect the skin for one or 
two inches on each side of the incision and cut away the muscles 
covering the neural arches of the vertebre from the third cervical to 
the seventh or eighth thoracic inclusive. 
Remove with bone-forceps the neural arch of one of the last 
cervical vertebra and find the spinal nerve emerging from the inter- 
vertebral foramen. Isolate the nerve for a short distance, then 
proceed craniad, removing the neural arches on one side and isolat- 
ing the nerves until the third has been uncovered. The ganglion of 
the second nerve should be sought among the muscles on the dorsal 
surface between the atlas and axis, and after it has been isolated the 
