43 



A discussion followed the paper, iu whicli the President adduced some 

 interesting facts on the question of absorption, which was shown to occur 

 in the advanced larva; of this insect. The casting of the antlers of deer is 

 due to similar cause, viz., absorption of the blood. 



Meeting held in the Medical School, Park Street, March 10th, 1890. 

 Professor de Burgh Birch, M.D., CM., F.E.S.E. (President), in the chair. 



THE PREPARATION OF BRAIN TISSUE FOR SECTION CUTTING. 

 PROFESSOR BIRCH. 



The first part of the meeting was devoted to an outline description of a 

 number of methods. Brain tissue being of such soft structure and so soon 

 fractured, gives rise to many difficulties in preparing so as to get it into a 

 condition of toughness and elasticity for cutting. The first method was 

 the use of chromic acid of 1 per cent, solution downwards, but the 

 disadvantage occurred that the chromic did not readily penetrate, but 

 formed an "incrustation on the outside ; the chromic also caused a green 

 precipitate, which interfered with successful staining. The second method 

 was in the use of Miiller's fluid in the proportion of I per cent, to J per 

 cent. Professor Hamilton's method was the use of bichromate of ammonia 

 of \ per cent, solution upwards. Another method was the use of gum 

 and sugar, one part saturated solution of gum and a 'quarter its bulk of 

 saturated cane sugar. Good results were obtained by these methods, but 

 the time which they take was a disadvantage, especially in cases of ^Josil- 

 mortem. The most successful method was that of Mr. Bevan Louis, and 

 which has yielded in his hands such excellent results. The portion of 

 tissue to be cut is first frozen into a block on the freezing microtome, the 

 sections are then cut, and placed in a :| per cent, solution of osmic acid for 

 two or three minutes, so as to fix the tissue. It is then placed on a glass 

 slip and stained by a fluid of \ per cent, solution aniline blue-black, the 

 superfluous stain is washed away, and the section is ready for mounting. 

 The whole process can be done within half-au-hour, a great advantage 

 over the other methods, which take weeks. In the laboratory Mr. Louis's 

 method was practically demonstrated, several sections were cut and 

 examined under microscopes, along with previously prepared slides of 

 brain structure. The meeting was exceedingly interesting, especially^ to 

 those members who were present at the President's address at the opening 

 of the session. 



Meeting held in the Library of the Philosophical Hall, March 17th, 

 1890. H. Bendelack Hewetson, M.RC.S., F.L.S. (Vice-President), in the 

 chair. 



EXHIBITION OF INSECTA. 



Mr. Hewetson exhibited and described living specimens of some 

 extraordinary sand beetles, obtained by him in the desert near Ismalia, 

 Egypt, where they were very plentiful. What is most remarkable about 



