154 



SUMMABY OF CUKRENT RESEARCHES RELATING TO 



to have the water kept clear. Whilst engaged in the prosecution of 

 a research into the minute anatomy and histology of Patella vulgata, 

 I found that owing to the granular character of the liver and 

 nephridia of that mollusc, it was almost impossible to keep the water 

 pure and free from granular debris, entailing constant journeys to 

 and from the sink, with the risk of disturbing and destroying the 

 dissection by the pouring off and renewal of the water. I accordingly 

 devised a form of dissecting trough which has answered its purpose 

 very well. 



It consists (fig. 37) of a long box of zinc or tin (preferably the 

 former) divided into three compartments. The central division A 

 is the largest ; the two end divisions are of much smaller size, equal 



Fig. 37. 



to each other, however. The partition between A and C has a slit s s' 

 about 1/2 in. from the top ; that between A and B does not quite 

 reach the bottom of the trough. Into compartment C a water pipe 

 w opens with a stop-cock t in the position indicated ; from com- 

 partment B an escape pipe w' passes off. The pipe w is in com- 

 munication with a water tap by means of guttapercha tubing, iv' by 

 the same means with the sink. In compartment A a loaded block of 

 paraffin is placed, the thickness of which varies with the size and 

 depth of the dissection. The block is made so as to leave a clear 

 space of half an inch between it and the sides of the trough. When 

 the stop-cock t is turned on, the water flows in, fills chamber C, over- 

 flows into A when it has reached the level of the slit ss', fills 

 chambers A and B, escaping by the pipe w'. The direction of the 

 current of water is indicated in the sketch by the arrows. The water 

 is of course always kept at the same level by the inflow ; the arrange- 

 anent of the slits in the partitions, however, tends to cause the debris 



