DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS 8l 



Polyodon this was a very simple matter; while with the Lepi- 

 sosteida^ which have such a bulwark of armor it was necessary 

 first carefully to remove entirely two or three rows of scales a 

 little back from the shoulder girdle. Great care should be 

 exercised in this operation for the delicate longitudinal lym- 

 phatic trunks are very firmly attached to the scales by connec- 

 tive tissue. When this is completed the body can be severed 

 as easily as Polyodon. Usually the blood vessels of Polyodon 

 were first injected from the cut aorta, but with the Lepisosteidas 

 this was not deemed necessary. With the Lepisosteidas the cut 

 ends of the dorsal, ventral, and one of the lateral lymphatic 

 trunks were first plugged with cotton, and the injection was 

 made from the remaining lateral trunk. Since no dorsal and 

 ventral lymphatic trunks were found in this region in Polyodon 

 it was only necessary to stop up one of the lateral trunks and 

 inject from the other. After the cephalic sinus and its poste- 

 rior connections had been worked out in Polyodon it was found 

 that a more satisfactory injection of the cephalic trunks could 

 be obtained by injecting the so-called cephalic lymphatic trunks 

 forward, from a point designated by {x) in Fig. i. During the 

 summer months the heat was so intense at Cairo that the gelatin 

 injecting mass in the vessels would not solidify unless the head 

 was first placed in a bath of ice water. When once the mass 

 was hard and the specimen placed in formalin it was found that 

 no amount of summer temperature would liquefy it. 



All the injected microscopic preparations were hardened in 

 formalin, run up the alcohols, and mounted in xylol-balsam. 

 The material for sectioning was fixed in Tellyesniczky's potas- 

 sium bichromate-acetic mixture, imbedded in paraffin, cut 6 to 

 lo fx thick, stained in either Heidenhain's iron h^ematoxylin or 

 Hansen's hsematoxylin plus 2 per cent, glacial acetic acid,^ and 

 counterstained in a concentrated alcoholic solution of orange G 

 plus a small per cent, of acid fuchsin. 



' The object of adding the 2 per cent, glacial acetic to Hansen's solution was 

 to do away with the precipitate which is always formed. The sections thus 

 stained are red, but rapidly turn to a brilliant blue when placed in tap water that 

 is alkaline. Formerly hiemalum was used for a simple hsematoxylin stain, but 

 my experience has been that the product as sold commercially varied so much 

 that it could not be relied upon, and that Hansen's solution was superior to the 

 strongest haemalum. 



