POPULAR MISCELLANY. 



7'5 



roof of a cave and dripping slowly to the 

 floor beneath. In cases where the water 

 filters sufficiently slowly or evaporation is cor- 

 respondingly rapid, the deposit of lime car- 

 bonate from the roof takes at first the form 

 of a ring around the outer portion of the 

 drop, a natural consequence of the evapora- 

 tion of a suspended drop of liquid. This 

 process may go on until the ring becomes 

 prolonged into an elongated cylinder or tube, 

 the diameter of which may not exceed five 

 millimetres, though usually ranging from five 

 to ten, and of all lengths up to fifty centi- 

 metres. In exceptional cases this length 

 may be exceeded, but owing to the delicacy 

 of the material the stalactite usually breaks 

 from its own weight and falls to the floor 

 before the length of -even ten or fifteen cen- 

 timetres is reached, to become imbedded 

 in the stalagmitic material there forming. 

 Lengths of even these dimensions are com- 

 paratively rare, for the reason that the tube 

 becomes shortly closed, either as its upper 

 or lower end, usually the upper, and all 

 growth from the extremity alone ceases, sub- 

 sequent depositions being wholly exterior 

 and taking place in the form of concentric 

 coatings of the carbonate on the outer sur- 

 face and at the same time from the top. 

 There is thus formed around the original tube 

 a compact cylindrical mass, in its typical 

 form, constricted at the point of attachment, 

 but thickening rapidly and then tapering 

 gradually into an elongated cone. The ma- 

 terial of the stalactites is not always wholly 

 carbonate of lime, but in some cases thin 

 intervening coats of iron disulphide are met 

 with. Through a kind of crystallization the 

 material sometimes undergoes a distinctly 

 fibrous arrangement, but oftentimes the 

 structure is granular throughout. 



Snake-bite Antitoxine. At a recent 

 meeting of the Royal Society of Edinburgh 

 Prof. Fraser delivered a lecture embodying 

 some extremely valuable and interesting data 

 obtained by him during several years of ex- 

 perimental work on an antidote for snake 

 poisons. The principles utilized by him are 

 similar to those employed in the antitoxine 

 treatment of diphtheria and in vaccination 

 for smallpox. He first immunized an animal 

 by repeated small doses of the snake poison, 

 slowly increasing the quantity, until the ani- 



mal was taking at a single dose many times 

 the minimum lethal amount for a non-im- 

 munized individual. He then injected into 

 another animal some of the blood serum 

 from the immunized case, and found that 

 this prevented any ill effects from a subse- 

 quent injection of venom. Still a third ani- 

 mal was given an injection of pure venom, 

 and, when distinct symptoms of poisoning 

 appeared, was treated with the immunizing 

 serum, with the result that the symptoms of 

 poisoning disappeared and no ill effects fol- 

 lowed. When it is remembered that in 

 British India alone there are each year from 

 eighteen to twenty thousand deaths caused 

 by snake-bite, the great beneficence of this 

 discovery is apparent. Prof. Fraser is at 

 present immunizing a horse, but is having 

 some trouble, owing to the difficulty of pro- 

 curing the snake- poison in sufficient quantity. 



Unsanitary Filters. For many years be- 

 fore any positive connection was established 

 between typhoid fever and a specific micro- 

 organism it was known that this and other 

 diseases were in some way connected with 

 the composition of the drinking water pre- 

 viously consumed by the patient. By chem- 

 ical analysis it was found that in almost all 

 such cases the water contained an excess of 

 organic matter ; it was accordingly inferred 

 that removing the organic matter would cor- 

 rect the trouble and obviate any further 

 danger; and filters were made with this end 

 in view. It is now known, however, that the 

 danger from waters containing much organic 

 matter lies not in the organic matter per se, 

 but arises from the fact that a large amount 

 of organic matter attracts and feeds a pro- 

 portionately large number of bacteria. It 

 has been proved experimentally that after a 

 filter of this class has been in use for some 

 time, water, in passing through it, becomes 

 much richer in bacteria, and even that ster- 

 ilized water passed through it is found 

 swarming with micro-organisms. The filter 

 collects the organic matter from the water 

 and with it some of the bacteria. This mass 

 of organic matter serves as an admirable 

 culture medium ; as the bacteria multiply, 

 they are taken up by the water as it passes 

 through the filter, so that, instead of serving 

 as a safeguard against disease, such filters 

 are really disease breeders. In order to be 



