ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 619 



observations of A. Agassiz on the translocation forwards of the rudi- 

 ments of the pelvic fins in the young larva of Lophius, as demon- 

 strating beyond any doubt that the Physoclisti have descended from 

 the Physostomi. 



Silver-reducing Animal Organs.* — The success of Drs. O. Loew 

 and T. Bokorny with vegetable cells induced the former to try and 

 see if the protoplasm of animal cells would not likewise have a silver- 

 reducing effect. Into between fifty and one hundred cubic centimetres 

 of a solution which contained about 5 per cent, of silver the author 

 placed the kidneys freshly taken from a frog or toad, with the 

 ventral side turned upwards ; the light was immediately cut off", but 

 within fifteen minutes the bright bands on the surface became 

 darkened, and in less than two hours were quite black. This very 

 remarkable reaction is only to be observed with living tissues. The 

 tissue may be seen under the Microscope to be traversed by black 

 dots, more or less closely packed together. If the kidneys are left 

 for twelve hours in the solution, a number of black dots may be 

 observed in the interior of the kidney, and especially in the neigh- 

 bourhood of such canals and other spaces as afford an easy means of 

 passage for the reagent. These experiments are sufficient to show 

 that living animal protoplasm can effect a reduction of silver. 



Effects of .Very Low Temperatures on Living Organisms. f — 

 Mr. J. J. Coleman and Prof. M'Kendrick have made some remark- 

 able experiments on the effects of low temperatures on living 

 organisms, particularly microbes, using for this purpose the cold-air 

 machinery invented by Mr. Coleman, which, in its ordinary working, 

 delivers streams of air cooled to about 80° below zero ( — 63° C), but 

 by certain modifications as low temperatures can be secured as have 

 yet been produced in j^hysical researches. 



The experiments consisted in exposing for hours to low tempera- 

 tures i)utrescible substances in hermetically sealed tins or bottles, or 

 in flasks plugged with cotton-wool. The tins or flasks were then 

 allowed to thaw, and were kept in a warm room, the mean tempera- 

 ture of which was about 80^ F. They were then opened, and the 

 contents submitted to microscopical examination. The general result 

 may be stated thus: — The vitality of micro-organisms cannot be 

 destroyed by prolonged exposure to extreme cold. It is clear, there- 

 fore, that any hope of preserving meat by permanently sterilizing it 

 by cold must be abandoned, for the microbes, which are the agents of 

 putrefaction, survive the exposure. 



Some of the experiments on which this conclusion rests are briefly 

 described. Meat in tins, exposed to 03° C, for six hours, underwent 

 (after thawing) putrefaction with generation of gases. Trials with 

 fresh urine showed that freezing at very low temperatures delayed tho 

 appearance of tho alkaline fermentation, but a temperature of 03^ C. 

 for eight hours did not sterilize tho urine. Samples of fresh milk 



• Pfliiger'H Archiv f. d. GoBammt. Phybiol., xxxiv. (1885) pp. 5'JG-GOl. 

 t Journ. of Anat. and PhyBiol., xix. (1885) pp. 335 44. 



