504 



Prof. S. Vincent. 



[Apr. 6, 



of animals and contains a fuller description of the microscopic structure of 

 the chromaphil bodies than has hitherto appeared. 



II. Methods Eviployed. 



For the study of the naked-eye anatomy of the mammalian chromaphil 

 tissues the following method (of Kohn and Stilling) has been adopted : — The 

 liver and alimentary tract are removed from the abdomen and a piece of 

 absorbent cotton soaked in a solution of potassium bichromate (3"5 per cent.) 

 is placed over the retroperitoneal tissues and left in situ for 6 to 12 hours. 

 At the end of this (or in some cases a longer or a shorter time) the adrenals, 

 aorta, vena cava, and subjacent and superjacent tissues are cut out as far 

 back as the bifurcation of the aorta and washed in running water for several 

 hours. The chromaphil bodies are then plainly seen, and still more plainly 

 if the whole preparation be placed in glycerine. They appear as dark 

 brown streaks, patches, or dots of varying size and shape (see text-figs. 1 

 to 11). 



Another method which gives good resQlts is to first cut out the abdominal 

 vessels and the adrenals with the accompanying tissues and lay the 

 preparation in a solution of potassium bichromate (3"5 per cent.). In rabbits 

 and cats it is recommended that the animals chosen for examination be not 

 too fat. 



It is sometimes desirable to make a little further dissection after the 

 action of the bichromate. To see the smaller bodies, a simple lens or a 

 dissecting microscope may be employed. It is best that fresh material should 

 be employed; but fairly good results may sometimes be obtained, even if the 

 animal has been dead for some hours before dissection. 



For the microscopical examination of the chromaphil cells and bodies in 

 the first instance, Kohn's fluid (potassium bichromate, .3-5 per cent., 90 c.c. ; 

 formol, 40 per cent., 10 c.c.) has been employed, or the bodies revealed 

 macroscopically by the application of bichromate have been washed, passed 

 through alcohol, and treated by any of the usual methods for microscopical 

 preparation. 



]5ut bichromate solutions, even witli the addition of a certain proportion of 

 formol, do not give the best results for detailed histological examination, 

 howsoever convenient they may be for identification of chromaphil cells. For 

 this reason, after the bodies have once ])eon carefully located by means of the 

 bichromate, from suljsciiuent specimens they have been fixed in corrosive 

 Huldiniate, Flemming's fluid, and other approved agents. The sections were 

 stained in various ways. For the small groups of chromaphil cells in the 

 sympiUhctic ^'ant,dia, it has Ihhmi necessary to emj)loy l)ichromate solution 



