450 J. F. ILLINGWORTH, 



For the study of the vascular system, several injection fluids were 

 used. With material which had been preserved in alcohol, good results 

 were obtained by injecting the alcoholic stains, haematoxylin, borax- 

 carmine etc. An advantage of these stains is that the color enters 

 the wall of the blood vessels quickly, and diffuses into the capillaries 

 mixing with the alcohol already there. "When a limited quantity of 

 dilute stain is used all the color enters the walls in a few minutes, 

 and the free alcohol may be run out. The stain penetrates only a 

 short distance into the coat of the blood vessel, sharply differentiating 

 it from the surrounding tissue. I have found only one injection mass 

 that works well on fresh material. This is a plaster-of- paris mixture. 

 It is made as follows : A tablespoonful of plaster is mixed with about 

 one-half a cup of water together with a little alcohol to keep the 

 plaster from setting too quickly and enough carmine solution to color 

 it a bright pink. This mixture must be made just before using and 

 stirred constantly or the plaster will settle to the bottom and harden. 

 The different injection masses that depend upon gelatin or glue for a 

 hardening agent do not work well in tissues containing so much water. 

 I have found them very unsatisfactory, as they run out of the vessels 

 too easily. The arterial system of Lucapina was injected from two 

 places, the ventricle and the buccal sinus. The walls of the ventricle 

 and aorta are so thin that only a slight pressure can be applied to 

 the injection mass, but by proceeding slowly the three branches of 

 the aorta with their capillaries were filled. The pedal and mantle 

 arteries were injected from the head sinus. Previous to injection the 

 animals were allowed to remain in stale sea-water for several hours 

 in order that they might be handled without the violent contraction 

 that necessarily follows any operation on the normal specimen. In 

 order to inject the venous circulation the anterior part of the mantle 

 was turned back, exposing the ctenidia, and a slight incision was made 

 in the afferent sinus of one of these and the mass forced into it with 

 a syringe. This one injection fills the whole venous circulation if suf- 

 ficient force be applied. 



The material for general dissection and for histological work was 

 killed, as fresh as possible, by injecting Van Gehuchten's fluid into 

 the vascular system. An opening was made into the buccal sinus, 

 from the under side of the neck, in the angle where it joins the foot 

 (Fig. 11 0). This can only be done by seizing the animal while ex- 

 tended. A pipette with a rubber tube attached to the upper end was 

 quickly pushed into the cut, and held in place so that it would not 



