May 5, 1898] 



NA TURE 



15 



probably be regarded as an extreme luxury by most 

 microscopists. 



Photography in colours, by all the current methods, is 

 well illustrated, many examples being of historic interest. 

 G. Lippinann, A. Lumiere, L. Vidal and H. Vv. Vogel 

 and several English exhibitors contribute to this section. 



" Photography as a science " refers apparently to what 

 might be called /«r^ photography to distinguish it from 

 npplied. But the distinction is neither clear nor precise. 

 This section includes apparatus for measuring the den- 

 sities of photographs, including opacities and blacknesses, 

 by Captain Abney, Hurter and Driffield, and Chapman 

 Jones ; besides sensitometers, actinometers, and similar 

 apparatus. Many results of the various treatments of 

 photographic plates are shown, such as the sensitising 

 for various colours, and the getting of an image free from 

 stain, &c., that it may be of definite opacity. E. Sanger 

 Shepherd shows an ingenious form of slit for spectro- 

 scopes, that is stated to be specially suitable for photo- 

 graphic use. 



The National Photographic Record .Association, that 

 has recently become established through the energy of 

 Sir Benjamin Stone, is well represented. Sir Benjamin 

 himself contributes twenty-one photographs relating to 

 the Houses of Parliament, every one of which is of 

 general interest. There are numerous other examples 

 of technical work to which we cannot refer in even the 

 most general terms, except to a case exhibited by the 

 Bolt Court Technical School of the London County 

 Council Technical Educational Board, which illustrates 

 the working of some of the most important photo- 

 mechanical processes arranged for educational purposes. 

 While there are some exhibits that claim attention 

 because of their novelty, these are the exception ; the 

 chief interest centres round the old rather than the new, 

 and the complete presentation of the capabilities of 

 photography in its numerous applications at the present 

 day. But those whose knowledge of photography is of 

 the general kind, and those who have not followed up its 

 <levelopments during the last few years, will find more 

 that is new, of both examples and processes, than they 

 will be able to appreciate in a single visit. Such an 

 •exhibition has never before been organised, and it must 

 obviously be impossible to arrange' another of similar 

 extent until after the lapse of several years. The 

 exhibition will close on May 14. 



MICRO-BIOLOGY AS APPLIED TO HYGIENE. 

 AT the Congress of Hygiene and Demography re- 

 ;^^ cently held at Madrid, many matters of scientific 

 interest and importance were introduced and discussed. 

 Unfortunately the papers were not printed and distri- 

 buted among the members, and as the majority were 

 read in Spanish, the discussions were curtailed. The 

 Section of Micro-biology as applied to Hygiene attracted 

 the largest share of attention. Among the more im- 

 portant contributions was that of Dr. Behring, who 

 announced that, as the result of experimental work with 

 the toxin and antitoxin of tuberculosis, he had isolated a 

 substance from the tubercle bacillus a hundred times 

 more powerful than Koch's tuberculin, and had obtained, 

 by passing the virus through the horse, an antitoxin 

 which he believed to be an efficient cure for the disease. 

 Experiments on a large scale are to be carried out at the 

 Berlin Veterinary University. Dr. A. Calmette, of the 

 Pasteur Institute of Lille, demonstrated in a highly 

 successful manner the prophylactic effect on snake-bitten 

 patients of serum of the blood of horses subjected to 

 srnall doses of the venom. For this purpose a rabbit was 

 mjected with a large dose of a mixture of venom of the 

 cobra, naja, and bothrops ; this proved fatal in twenty 

 minutes. Two rabbits were then injected with the pro- 

 NO. 1488, VOL. 58] 



tective serum, and in ten minutes each received a dose of 

 the mixture equal in amount to that which killed the 

 first rabbit. These rabbits appeared to suffer no ill- 

 effects. Further experiments gave unquestionable evi- 

 dence as to the prophylactic property of the serum, 

 which is easily prepared and retains its protective 

 power for an indefinite period. Great interest was 

 evinced in the paper read by M. Nocard, of the Alfort 

 Veterinary School, and delegate of the F'rench Academy 

 of Medicine, describing a method of cultivating the 

 microbe of pleuro-pneumonia of cattle, the demonstration 

 of which had baffled the efforts of bacteriologists for 

 nearly half a century. This destructive disease of cattle is 

 communicable only by cohabitation, and heretofore has not 

 been communicated to animals of other than the bovine 

 species. As long ago as 1850, Willems had established 

 the fact that the virus existed m the liquid exuding from 

 affected lungs, and laid down rules for a protective in- 

 oculation which has been regarded to a great extent 

 efficacious. His method was to mtroduce into the 

 subcutaneous connective tissue of the animal to be pro- 

 tected a drop of the serosity from an affected lung. The 

 necessity for having an absolutely fresh lung from which 

 to obtain the inoculating material renders Willem's 

 method very inconvenient and often impracticable. It 

 is hoped that the discovery of the specific microbe and 

 the power of cultivating it for indefinite periods, indepen- 

 dent of animals suffering from the disease, will afford the 

 means of providing an effectual, protective vaccine at all 

 times available when necessity for preventive inoculation 

 may occur. Heretofore, failure to cultivate the virus has 

 followed sowing in all ordinary media in air or in vacuo^ 

 and no method of staining has been successful in demon- 

 strating the virus. Nocard and Roux have, however, ap- 

 plied with success the plan adopted by Metchnikoff on the 

 toxin and antitoxin of cholera. Very thin-walled capsules 

 of collodion, rendered sterile by heat, are filled with sterile 

 bouillon, sown with a very small quantity of virulent 

 matter from a fresh pleuropneumonia lung and hermet- 

 ically sealed. The capsules are then inserted into the 

 peritoneal cavity of a rabbit. The collodion wall proves 

 an absolute barrier to the egress of the microbe and to 

 the ingress of the cells of the animal, which ordinarily 

 have a destructive effect on each other. The wall, how- 

 ever, is permeable to liquids and dissolved matters. Pro- 

 ducts of the microbe pass out, and sometimes prove fatal 

 to the animal ; while it is usually found that products of 

 the animal body, favouring the growth of the microbe, 

 pass inside the capsule, so that after a longer or shorter 

 period, according to the nature of the microbe and the 

 animal, a rich culture is found inside the capsule. The 

 microbe of pleuropneumonia thus cultivated is exceed- 

 ingly minute. When examined under a very high power 

 (2000 diameters magnification) the culture shows in- 

 numerable refractile, motile specks, so fine that, even after 

 staining, their form cannot be exactly determined. 

 Experiments with cows indicate that subcutaneous 

 inoculation of small quantities of these cultures afford 

 protection from the disease. Another interesting fact in 

 connection with these experiments, is the discovery that 

 if collodion capsules filled with sterile bouillon be inserted 

 into the peritoneal cavity of the rabbit or the cow, and 

 remain there for fifteen to twenty days, they are found to 

 contain a medium suitable for cultivation of the microbe 

 in vitro. Beyond the definite results in relation to the 

 special disease under consideration, facts elicited con- 

 cerning the method of providing favourable culture media 

 would appear to have a broad significance. 



Among the most novel suggestions for the application 

 of bacteriological science were those of Dr. E. Vallin, of 

 the F"rench Academy of Medicine, who drew attention to 

 the existence of saltpetre on the walls of dwelling-houses, 

 and its ill-effects on the health of the dwellers therein. 

 Dr. Vallin states that the salt is produced by nitrifying 



