1 34 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



Mounting in Canada Balsam. — Being an 

 amateur mounter I took an interest in Mr. Under- 

 bill's article in lasi month's number of Science- 

 Gossip on tbe "Preparation of Insects for Micro- 

 scopical Examination," and have no doubt that by 

 the time this series of articles is concluded I shall 

 have obtained many useful hints, but at the same 

 time I think I can myself give a few hints in return, 

 particularly with respect to mounting in Canada 

 Balsam. Mr. Underhill advises the use of test-tubes, 

 in which to keep the Canada balsam. I have never 

 used test-tubes myself, but cannot believe they are 

 either so handy or cleanly as two-ounce wide-mouthed 

 capped bottles, to be obtained at is. each. The 

 balsam is applied by means of a small brass rod 

 drawn to a point, and always kept in the bottle ready 

 for immediate use ; a knitting needle will also answer 

 this purpose, but will require cleaning occasionally. 

 If, however, very large covers are used, I would then 

 advise a glass syringe, as recommended by Dr. 

 Carpenter. 



Then again, I cannot say I like the use of clips, 

 and never employ them if I can possibly help it. The 

 pressure of the clip causes the covering glass to 

 "dish," and when the clip is eventually removed the 

 cover springs back to its original position, causing a 

 suction all round the edge, and in case of "fluid" 

 mounts a running in of the cement ; an apparent 

 shrinkage taking place when balsam is used, but 

 this is easily remedied. 



When mounting in fluid I prefer to have the cell 

 quite as deep as the object, and when the cover is 

 put on, if the superfluous fluid be removed by means 

 either of bibulous paper or a damped camel's-hair 

 brush, it will be found that the cover is held down by 

 suction sufficiently firmly to enable a very thin coat of 

 cement on and just over the edge, to be dabbed on by 

 means of a brush ; when this cement is dry the slide can 

 be further washed, as directed by Mr. Underhill, and 

 extra coats of cement applied by means of the turn-table. 



I doubt if balsam would ever set without some 

 heat, but at the same time I think it very risky to 

 apply heat by means of a lamp. My own method is 

 to mount without heat, and after the lapse of a day 

 or two to place the slide upon the top of a hot- water 

 cistern for a bath, the heat of which can be moderated 

 as desired by means of slips of wood placed under the 

 slide, which will have to remain there for a week or 

 even longer, according to the size of covering glass 

 and thickness of balsam. 



I could say a little on "coaxing" air-bubbles out 

 of Canada balsam ; there is a knack in getting rid of 

 these pests. In many cases, however, the bubbles are 

 merely vapour of benzole, and will disappear spon- 

 taneously in the course of half a day or so, being 

 re-absorbed by the balsam. — //. M. 



The Thallus of Diatoms.— In a recent number 

 of the " Journal de Micrographie," Dr. M. Lanzi has 

 a note on this subject, in which the thallus, or gela- 

 tinous stem or stipes, of certain species of diatoms 

 is carefully delineated. These gelatinous stems, he 

 says, are produced by the accumulation of plasma 

 within the cells, which takes place to such an extent 

 as to issue from the pustules. This plasma plays the 

 part of an organ of vegetation, and therefore does not 

 properly afford either by its presence or absence any 

 distinction of species. It may furnish nutriment to 

 the young diatoms, or even may serve to distribute 

 the species by dividing into parts, which are carried 

 off by the water. Dr. Lanzi thinks that all genera 

 founded upon the character of the thallus and its 

 form should be abolished. 



Microscopic Organisms in Blood. — Under the 

 title of "The Microscopical Organisms found in the 

 Blood of Man and Animals, and their relation to 

 Disease," Dr. T. R. Lewis, of the Army Medical 

 Department, and who is also Special Assistant to the 

 Sanitary Commissioner with the Government of India, 

 has published another small quarto work of about 

 ninety pages. It describes the various vegetable 

 organisms found in blood during splenic fever. 

 Pneumo-enteris of the pig, recurrent fever, &c. ; the 

 relation of microphytes to disease ; vegetable organ- 

 isms in healthy blood ; spirilla and their supposed 

 relation to disease ; protozoa in blood, such as 

 flagellated organisms, nematoids and their embryos, 

 Filaria sanguinis-hominis, &c. This is one of the 

 most thoughtful of Dr. Lewis's works. 



Effects of Starvation. — From the office of the 

 Superintendent of Government printing, in Calcutta, 

 there has just been issued Dr. Cunningham's report 

 on "Certain effects of Starvation on Vegetable and 

 Animal Tissues," in which we have detailed from 

 microscopical examination, and experiment, the full 

 effects of a deficient supply of nutritive material both 

 on animals and vegetables. In the latter this is 

 chiefly manifested by the growth of microscopic 

 fungi. The chapter on "Phenomena observed in 

 the post-mortem examinations of cases of famine — 

 diarrhoea, and dysentery," is a most valuable essay to 

 Indian pathologists particularly. We hope Dr. 

 Cunningham may be able to continue his important 

 researches with the same success as heretofore. 



The Colour of St. Paul's Cathedral, etc. 

 — Last year Professor Paley contributed an article to 

 Science-Gossip suggesting that the dark colour of 

 the stone-work of St. Paul's and other churches 

 might be due to organic agency. No answer was 

 given to his queries. The " American Quarterly 

 Microscopical Journal " states that Professor Leidy 

 finds that the black or smoky colour found on old 

 walls in narrow shaded streets is caused by an alga 

 closely resembling Protococcus viridis. It may be 

 this plant in a particular stage, but Professor Leidy 



