BLOOD-VASCULAR SYSTEM OF THE LORICATI 33 



its action toward gelatin is favorable, hardening it considerably. 

 The coats of the eye are fixed in perfect shape, and such deli- 

 cate organs as the kidneys are quickly hardened, so that one 

 can cut cross-sections with a knife, which is a great help in 

 tracing out the renal-portal system. 



If a histological injection is required, slit the siims venosus 

 and wash out the blood vessels, cephalad, from the dorsal aorta ; 

 then inject with an aqua or thin gelatin Berlin blue mass, or 

 wath Hoyer's yellow chromate mass, freshly prepared. The 

 mass is allowed to set and the injected organs are thrown in 

 toto into jVUiller's fluid, or better still, cut up into small pieces 

 and thrown into any well known fixing fluid that will not extract 

 the colors. Injected material thus fixed can be kept some 

 months in alcohol, but it is best to imbed as soon as possible. 



If the bile vessels are to be injected, it can be accomplished 

 by slitting the ductus choledochns, near its exit into the intestine 

 or pyloric c^ca. A hypodermic syringe filled with the Berlin 

 blue mass is inserted into the duct, toward the gall-bladder, fill- 

 ing first the bladder, then the hepatic ducts, and finally, if suc- 

 cessful, the gall-capillaries. 



III. HISTORICAL REVIEW. 



To Duverney (13),* in 1699, 62 years after the discovery of 

 the blood-vascular system by Harvey, and 38 years after the 

 discovery of the capillaries by Malpighi, belongs the honor of 

 first explaining the structure of the fish heart ; and 2 years later 

 (14) he described and figured the circulation in and about the 

 gills of the carp ; he erred, however, in finding but one branchial 

 vessel in a branchial arch. Monroe (48) in 1787, was the first 

 to describe correctly the circulation in the gills. He injected 

 the ventral aorta and examined the gill-filaments under a micro- 

 scope ; he also noticed the efferent branchial vessels, uniting to 

 form the carotids, cceliaco-mesenteric, dorsal aorta, and the sub- 

 clavians, and observed the coronary and other vessels coming 

 from the ventral ends of the efferent branchial vessels ; as well 

 as the jugular, portal, and renal-portal systems. According to 

 Miiller (50), Albers (i) in 1806, was the first to notice the cho- 

 roid gland of the eye, and observed that the vessels in the cho- 



* All figures in brackets refer to bibliography at the end of the paper. 



