1893.] MICROSCOPICAL JOURNAL. 23 



to laboratory use, and precautions have to be taken to prevent ex- 

 plosions. The freezing ciiainber of the microtome must be shal- 

 low (3-16 incli will do) so that the gas which, by its own evapo- 

 ration, l)ec()mes frozen solid in it, may continue U) freeze the speci- 

 men above it. The brass plate above the chamber siiould be thin 

 but still strong enougii to stand consideral)le pressure, and tiie 

 floor of the chamber should be of hard rubber in order to reduce 

 as much as practicable the loss of cold. When these dilbculties 

 have been overcome, the metiiod combines cheapness with elli- 

 ciency, and enables one with small expenditure of time to examine 

 all tlie organs from an autopsv and to complete the diagnosis wliile 

 the case is fresh in miiul. 



MUKOSCOPK AL MANiriLATlON. 



Simple Method of Substituting Strong Alcohol for a 

 Watery Solution in the Preparation of Specimens. — Pro- 

 fessor \\ . A. liaswell, the well kncnvn microscupist, describes 

 in the proceedings of the Linn. Society of New South Wales, 3d 

 series, vol. vi, the following method: " Lo Bianco has. in the 

 last part of the ' Mittheilungen aus der Zoologischen Station zu 

 Xeapel,' published an account of the methods which he follows 

 in preparing those marvellous specimens of marine invertebrates 

 for which the station has long been famous all over the world. 

 Many of the methods described have now been known to zoolo- 

 gists for some time, /. e. , many of the methods of killing and 

 fixing; it is more, perhaps, on account of the information which 

 it gives us, as the result of a long series of trials, as to what re- 

 iigents are best adapted to each special group, with the best 

 modes of application in each case, than as giving any entirely 

 new formuUe, that the paper is of value. 



As is well known, marine animals of ditferent groups require 

 to be dealt with in very different ways in order tiiat we may pre- 

 serve them in anything approaching to their natural form. Some 

 may be taken by surprise, if we may use the expression, and 

 killetl so suddenly by some powerful poison that they remain in 

 a life-like shape. Others must be narcotized or paralyzed by 

 some such reagents as chloroform, weak alcohol, or chloral hy- 

 drate, before the killing and fixing agent is used. 



Whatever be the method of killing and fixing emploved, there 

 is in all delicate organisms a difficulty experienced in preventing 

 shrinkage during the latter processes which the specimens have 

 to undergo before reaching the strong alcohol stage. In the most 



