150 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tube, which is provided with a piuchcock V. Whcu the steam passes 

 out in a jet, the lamp is removed, V is closed, and the vessel R cooled 

 slowly by a wet sponge, by which means a vacuum is produced, and 

 the mercury rises above 70 cm. The air is thus drawn out of the 

 prejiaration and the parafl&n penetrates. In half an hour the air may 

 be I'eadmittcd. 



Rapid Imbedding.* — In his studies on Limnhis J. S. Kingsley 

 adopted the following method of imbedding large numbers of speci- 

 mens at once, thus effecting a considerable saving of time. The same 

 method is applicable to any easily oriented object. 



The embryos were taken from absolute alcohol and transferred to 

 chloroform and then impregnated with paraffin in the normal way. 

 When at last they were in pure paraffin they were transferred with a 

 quantity of paraffin to a flat-bottomed watch-glass, and, the paraffin 

 being kept in a melted condition, the embryos were arranged in a 

 symmetrical position, the heads all pointing the same way and con- 

 siderable space left between them. When arranged, the whole was 

 allowed to cool, and then each embryo was cut out, together with a 

 parallelogram of the surrounding paraffin, the longer axis of which 

 corresponded with the axis of the embryo. The head end was marked, 

 and then the crystal was slightly warmed, which allowed the little 

 strips of paraffin to be readily removed. When it was desired to cut 

 one of the specimens, it was a comparatively easy operation to place it 

 in any desired position and fasten it by means of a hot needle on the 

 end of a larger piece which fitted the clamp of the microtome. 



The author tried various killing and hardening reagents (Klein- 

 enberg's fluid, Perenyi's fluid, Miiller's fluid, chromic acid, Merkel's 

 fluid, corrosive sublimate, and osmic acid), but for sections he had 

 the best results with the use of alcohol of various gi'ades, beginning 

 with 50 per cent, and ending with absolute. For surface views 

 nothing excels osmic acid used for about ten minutes in a ' 1 per 

 cent, solution. 



Caldwell's Automatic Microtome.— Mr. W. II. Caldwell's very 

 novel and ingenious instrument has effected a revolution in the art of 

 section-cutting, especially where it is desired to cut a very large 

 number of sections of equal thickness in a very short time, and to 

 insure their arrangement in tlieir proper consecutive order and A\'ith 

 the same side upwards. It may be easily made to deliver in one 

 continiious ribbon sections at the rate of 100 per minute, and when 

 driven by means of a motor, such as the water-motor used for it at 

 Cambridge, more than double this number can be obtained. 



The general form of the instrument, which is supported on a 

 heavy iron frame 3G in. long, 8 in, wide, and 11 in. high, resting on four 

 feet, is shown in fig. 29, the object-holder with its carrier (in enlarged 

 view) at fig. 30, and the top plate of the microtome, with object, knife, 

 and belt, at fig. 31. 



The carrier, with the object, moves backwards and forwards be- 

 neath the razor (any ordinary razor does), whicli remains stationary 



* Soieuce Record, ii. (1884) p. 2G9. 



