
788 THE AMERICAN NATURALIST. | [Vor. XXXVI. 
lining cells. Before injecting the solution of silver nitrate it 
was necessary to remove the chlorides from the vessels by 
irrigating them with a 5 per cent solution of potassium nitrate. 
This solution was followed by a ¥% per cent solution of silver 
nitrate, and after a few moments this was removed and the 
tissues fixed by the injection of 95 per cent alcohol Small 
pieces of the several organs were dehydrated, cleared in creo- 
sote, and mounted. The contraction of the intrinsic muscles 
of the vessels renders complete injection very difficult, and to 
obviate this difficulty by dilating the vessels the injection fluids 
and the water in which the squid were kept were saturated with 
amyl nitrite. This method was not uniformly successful. 
The general arrangement of the vascular system of the 
squid will be recalled by a glance at the diagram (Fig. 1) of 
obs. t 








205 cs ph ss aa A 
i ao bre cd => pp indi ` 
RYC 
] us 
br's os UC 
brh pe: 
Fic. 1. — Diagram of the vascular system of the squid as seen from the left. aa, anterior aorta; 
ork, branchial heart; őrs, brachial sinus; cs, cerebral sinus; A, heart; zs, inner buccal 
sinus; zs, nephridial sinus; 04s, outer buccal sinus ; os, optic sinus ; p posterior aorta; 
pc, postcava; pf, peripheral heart; ss, salivary sinus; vc, vena cava. 
the system seen from the left. Arterial blood enters the one- 
chambered heart from the gills through the two branchial veins 
and is forced out through the anterior, posterior, and genital 
aorte. The anterior aorta forks near the head, and each branch 
bears a muscular enlargement, called a peripheral heart, at the 
point where it breaks up into the branches which supply the 
head. The two branches of the posterior aorta which pass out 
of the mantle to the fins also have peripheral hearts. The 
latter are vascular sphincters, which probably contract synchro- 
nously with the mantle, and so prevent the transmission of an 
excessive blood pressure to the extra-pallial vessels. The blood 
returning from the arms through the brachial veins reaches the 
brachial sinus, which is connected with five sinuses, that partially 
enclose the pharynx, the eyes, and the brain. These sinuses 
open into the anterior vena cava, which also receives a ven 
from the sinus that encloses the salivary gland. The anterior 
