October 7, 1921] 



SCIENCE 



331 



method with some of those of the celloidin 

 technique. 



From ordinary series of paraffine sections the 

 parffine is removed in xylol, the slides being 

 transferred with great care to 100 per cent, 

 alcohol and then to 1 per cent, parlodion from 

 which they are removed slowly one by one 

 and placed in 80 per cent, alcohol, an old 

 method for securing sections to the slide espe- 

 cially for preventing embryonic membranes 

 from floating about. After staining by any 

 method and dehydrating, the slides are re- 

 moved singly from 100 per cent, alcohol, 

 placed in a horizontal position, and the sec- 

 tions quicMy and evenly flooded with 2 per 

 cent, parlodion. About 10 to 14 drops, from 

 an ordinary 2 c.c. pipette, placed in two rows 

 and allowed to stand one to two minutes un- 

 covered were found to form a film of very uni- 

 form thickness and of sufficient firmness to 

 be hardened without wrinkling when slipped 

 into 80 to 90 per cent, alcohol. The proper 

 degree of drying is indicated by a minute 

 rippling of the surface of the celloidin. The 

 slide is again dehydrated, care being taken 

 not to use alcohol strong enough to dissolve 

 the celloidin; and then cleared in a mixture 

 of 40 per cent, beechwood creosote in xylol, 

 followed by plain xylol. Creosote alone clears 

 quite as well but does not flow as readily as 

 the mixture which, moreover, clears from 95 

 per cent, alcohol. Such slides may be thor- 

 oughly drained in the air for several minutes 

 before covering in the ordinary way with 

 balsam and a cover glass. 



It should be noted that the parlodion must 

 be applied evenly so that the balsam will dry 

 without the formation of large air bubbles. 

 The latter can be entirely avoided. Further- 

 more, thinner films suitable for use with oil 

 immersion objectives can be obtained by using 

 a solution of parlodion somewhat more dilute 

 and less in quantity. 



By this method sections of the most delicate 

 structures are imbedded in and under a per- 

 fectly transparent, unstained layer of celloidin 

 so tough and resistant that sufficient pressure 

 may be applied to the cover-glass to crush it 

 without the least injury to the tissue. Slides 



so treated can not be distinguished from or- 

 dinary slides. J. A. Long 

 Zoological Labokatokt, 

 University of California, 

 Berkeley, California 



QUOTATIONS 



THE BRITISH ASSOCIATION 



The Edinbu,i-gh meeting of the British 

 Association for the Advancement of Science 

 came to a successful end yesterday. It was 

 the largest in numbers for many years; and 

 although the deficit on the accounts of last 

 year made it impossible to devote money from 

 current funds to research, there is a better 

 prospect for the immediate future. Thirteen 

 sections sat concurrently during the greater 

 part of the week. It can not be pretended that 

 all the proceedings conformed with the nor- 

 mal definition of science. Humor in school 

 children, episcopal opinions on citizenship, 

 the relative merits of Latin and Esperanto, 

 and the history of Old Edinburgh are worthy 

 occupations of the human mind, but lie some- 

 what uneasily with sterner subjects. The 

 general committee showed a marked reluc- 

 tance even to consider the advantages of a 

 stricter definition of the scope of the asso- 

 ciation, and the adherents of sections more 

 loosely attached to experimental science very 

 naturally opposed proposals which they feared 

 might lead to their extinction. On the other 

 hand, the policy of the Council in arranging 

 intersectional discussions on topics of wide 

 interest was warmly approved in theory. In 

 practise it led to some of the largest audi- 

 ences in the history of the association. It 

 was possible to give in our columns only 

 slight indications of the general purport of 

 the discussions on the structure of molecules, 

 the age of the earth, and instinctive behavior ; 

 but our special correspondent laid stress on 

 the wide interest taken by the members of the 

 association in these deeper problems. 



Sir Edward Thorpe, the president, was un- 

 fortunately prevented by illness from all but 

 a formal attendance on the last two days 

 of the meeting. But his opening address, read 

 for him by the principal of the university. 



