Journal of Applied Microscopy. 



Journal of 

 Applied Microscopy. 



Issued Monthly from the Publication Department 



of the Bausch & Lomb Optical Co., 



Rochester, N. Y. 



L. B. ELLIOTT, Editor. 



Address all communications to 



Publication Department, 



BAUSCH & LOMB OPTICAL CO., 



Rochester, N. Y. 



ONE DOLLAR PER YEAR. 

 To Foreign Countries - - $1.25 Per Year. 



Entered at the Post-office, Rochester, N. T., as second-class matter. 



MAY, 1898. 



EDITORIAL. 



As there is at the present time no 

 directory of the users of the microscope, 

 the question arises whether it would 

 not be of material benefit to those inter- 

 ested, biologists, histologists, patholo- 

 g-ists, petrographers, chemists and all 

 classes who in any way require the 

 microscope, to have such a directory. 



The Journal desires an expression of 

 opinion on the subject with a view of 

 publishing as complete a directory as 

 possible for 1899 if sufficient encourage- 

 ment is received. 



A good directory would furnish a 

 ready means of communication between 

 the users of the microscope, so that 

 exchanges of material and experience 

 might be readily effected. 



NOTES AND QUERIES. 



This space is intended for inquiries regarding 

 subjects not otherwise touched upon. Answers to 

 inquiries will be published over the signature of 

 the writer. 



Permanence of Stains. 



In reply to an inquirer, I wish to say 

 that the question he asks is one of deep 

 interest to me, as it must be to many 

 others, also those who are engaged in 

 making museum collections of a his- 

 tological and embryological nature. 



The defect of fading is caused mainly 

 by two factors: The chemical suscepti- 

 bility of the stain to fading; the manner 

 of mounting the specimen, whereby con- 

 ditions are produced favorable or 

 unfavorable to fading. 



The first factor I will not discuss 



beyond mentioning my observation that 

 the carmine stains and safranin seem 

 to be the most permanent colors. The 

 second factor is the key to the problem, 

 and two conditions must be taken into 

 account: First, the mounting medium; 

 second, the area of the specimen as com- 

 pared with the area of its cover glass. 



The usual mounting medium varies in 

 many particulars, some of which must 

 be very active in aiding or hindering 

 fading. Acidity is a common and fatal 

 defect in balsam. Other still undeter- 

 mined ingredients must also hasten 

 fading. 



Again, besides deleterious constituents 

 of the mounting medium itself, fading 

 is caused by the penetration of some 

 reagent (probably oxygen, chlorine, or 

 some other gas) beneath the edge of the 

 cover glass and through the balsam. 

 This occurs slowly and is performed by 

 diffusion, as is shown by the concentric 

 fields of fading which begin and. are 

 strongest at the edge of the cover and 

 which extend slowly inward or centri- 

 petally. Two remedies are suggested: 

 The ringing of the slide with some thick, 

 hard ring, and the use of large cover 

 glasses to prevent the encroaching gas 

 from reaching the specimen so quickly. 

 The first has seemed to be of value, 

 especially when Brunswick black was 

 used for the ring. The second has 

 apparently proved less useful because 

 the outer field of balsam is hard and 

 only permits of the entrance of the gas 

 by diffusion, while the central field in 

 which the specimen lies is still fluid 

 (vide any broken cover glass on an old 

 specimen), and here convection currents 

 hasten the penetration of the gas. The 

 following experiments are being carried 

 on in the Laboratory of Histology at 

 Princeton by the writer, and in them 

 the processes which in time usually bring 

 fading about are performed under exag- 

 gerated conditions, thus reducing the 

 time element and enabling us to learn 

 quickly facts concerning fading which 

 otherwise could only be acquired in long 

 years and at the expense of the ruin of 

 valuable collections made during these 

 same years. 



Specimens prepared alike in every 

 detail are submitted to the following 

 conditions and the results compared: 

 They are mounted in different media, 

 especially different balsams; they are 

 exposed to full sunlight, to room day- 

 light, and to darkness; they are exposed 

 in sealed jars to oxygen gas, to chlorine 

 gas, and other gases liable to be found 

 in the laboratory; they are mounted 

 under cover glasses of different diame- 

 ters. 



Ulpjc Dahlgren. 



Princeton, N. J. 



