CIRCULATORY SYSTEM OF THE GRASS-SNAKE. 618 



the snake most commonly dissected in the laboratories of this 

 country, no description of its vascular system has appeared since 

 the anatomical account of the blood-vessels in snakes written by 

 Schlemm (35) in 1827, which was based largely on Coluber 

 (i. e. Tropido7iotus) natrix and Trigo7ioGephalus inutus. This 

 account by Schlemm, although excellent in many respects, is by 

 no means complete, and, owing to the overlooking of the cerebral 

 carotid artery, the remaining arteries of the head are misinter- 

 preted. A great deal of work has been done, however, on 

 different parts of the circulatory system of this animal by various 

 authors. We are indebted to Ratlike for a valuable account of 

 its development (30) and also of the arteries of the head and 

 neck (31) ; the last is the best general account of these vessels in 

 snakes that has been written as yet. Hochstetter has dealt with 

 the development of the posterior veins (20) and of the blood- 

 vessels in general (22), Grosser and Brezina (19) with the 

 development of the veins in the head and neck, and Bruner (12) 

 with the veins and sinuses in the head of the adult. 



In addition to these works bearing directly on T. natrix, 

 Beddard (1-6) has added considerably to our knowledge of the 

 blood-vessels of other snakes, and the intracranial circulation has 

 been dealt with in the vertebrate series in general by De Vriese 

 (14) and Hofmann (24) and in reptiles by Dendy (13). 



The blood-vessels of the Grass-Snake were investigated by 

 means of the dissection of a number of injected specimens. The 

 injection fluid used for the main vessels was that recommended 

 by Kingsley (28), i. e., 



Corn starch and 2 per cent, chloral hydrate (each) 400 vols. 

 95 per cent, alcohol 100 vols, and Colour and glycerine (equal 

 parts) 100 vols. 



For the finer vessels a gelatine mixture advised by Tandler (36) 

 was used, i. e., 



5 gms. of gelatine in 100 c.c. of distilled water coloured with 



Berlin blue or carmine. 

 5-6 gms. of potassium iodide added slowly while warming 



gently. 



These are two very good mixtures, as the first will keep almost 

 indefinitely, and the second, with the addition of a few crystals 

 of thymol, will keep in a stoppered bottle for months, and, in 

 addition to being useable when almost cold, will withstand acids. 

 By mixing a quantity of the gelatine mass with about one-third 

 or less of its volume of the solid residue that settles to the 

 bottom of the starch mixture, an extremely useful general in- 

 jection mass is obtained. The latter mass, which flows very 

 readily if only slightly warmed, and sets firmly and fairly quickly 

 in 70 per cent, alcohol or in 4-5 per cent, formalin, was the one 

 most frequently employed in making the preparations for this 

 investigation. 



