724 
PROFESSOR T. J. PARKER OK THE 
venosus, and hepatic sinus. The renal portal veins may he separately injected 
from the caudal vein, in which case it is instructive to use a different colour to 
that employed for the cardinals. Owing to the extreme thinness of their walls a 
comparatively slight pressure is sufficient to rupture the renal portal veins. 
The lateral veins may be injected by opening the abdomen, cutting across one 
of the veins and pushing a tapering glass cannula into it far enough to prevent 
escape ; tying is inadmissible since the lateral veins cannot readily be dissected 
from the surrounding muscle. The cutaneous veins have to be separately filled 
in the same way. The jugular may be injected from the ventral end of the 
liyoidean sinus or from the precaval sinus by pushing the cannula beyond the 
valves. 
For all the above methods of venous injection, plaster of Paris may be used as 
for the arteries, but for accurate investigations it is advisable to employ a solution 
of gelatine coloured with precipitated carmine or Prussian blue. The vessels, unlike 
those of Teleosts, will bear a moderately high temperature (40°-50° C.) without 
injury. 
The whole vascular system may be more or less successfully filled by injecting from 
any branch of the coeliaco-mesenteric artery with gelatine coloured with Prussian 
blue, and, when the mass has passed the capillaries and filled the veins, withdrawing 
the syringe and injecting immediately, through the same cannula, with plaster of 
Paris coloured with vermilion ; this replaces the gelatine as far as the smallest 
arteries, but no farther, so that the arteries become filled with red and the veins with 
blue. # It is only by injecting in this way, so as to fill the veins from the capillaries, 
that I have ever succeeded in satisfactorily demonstrating the cerebral and myelonal 
veins. 
A very instructive preparation of the splanchnic vessels may be made by injecting 
from the ventral gastric artery and anterior lieno-gastric vein with red and blue plaster 
of Paris respectively, then removing the alimentary canal, and, after washing out its 
contents, distending with air and drying. When dry the intestine should be opened 
in one or two places to show the spiral valve and the intra-intestinal artery and vein. 
For making out the precise position of the chief vessels in relation to surrounding 
parts, as well as for settling many points left uncertain by ordinary dissection, sections 
of frozen specimens are extremely useful. I have prepared a complete series of 
transverse sections of an adult female, as well as horizontal and vertical longitudinal 
sections of the head and shoulders of other specimens. I have to thank Mr. W. 
Cunningham Smith, Secretary of the New Zealand Refrigerating Company, for allowing 
me to have my specimens frozen at the Company’s works, Burnside, near Dunedin. 
I may mention that fishes are far more difficult to freeze than mammals ; after six 
days’ exposure to a temperature of 20° F. (about —7° C.), my dog-fishes, which were 
* This method has been recommended by my friend Prof. H. F. Osborn, of Princeton (‘American 
Naturalist,’ vol. 19, 1885, p. 526, and ‘ Microsc. Soc. Journ.,’ vol. 5, 1885, p. 905). 
