METALLURGY. (STRUCTURE OF METALS.) 



In .1 subsequent address at the same congress 

 Dr. John McFadyean, principal of the Royal 

 Veterinary College, London, questioned Dr. 

 Koch's conclusions, giving his opinion that " there 

 >till remain reasonable grounds for regarding tu- 

 berculous cow's milk as distinctly dangerous to 

 human beings." He pointed out the fact that the 

 bacilli from the two diseases are indistinguish- 

 able, and said that he and other experimenters 

 had repeatedly succeeded in causing undoubted 

 tubercular lesions in cattle by the injection of 

 human tubercle bacilli. In conclusion he said: 

 " I earnestly hope that the congress will not in- 

 dorse the view that it is inadvisable to take any 

 measures to prevent the transmission of tubercu- 

 losis from the lower animals to human beings. 

 To justify the introduction of measures to that 

 end,' it is not necessary to contend that this is a 

 common method of infection, or that the danger 

 arising from milk can for a moment be compared 

 with that present in human sputum. The inhala- 

 tion of tubercle bacilli expelled from the bodies 

 of human patients is doubtless the great cause 

 of human tuberculosis, and every practicable 

 means of preventing infection in that way ought 

 to be employed. But at the same time we ought 

 not to concede to the milkmen the right to sell 

 us tubercle bacilli, even if we are assured that, 

 like Prof. Koch's experimental pigs, we have noth- 

 ing to fear beyond the development of ' little 

 nodules here and there in the lymphatic glands ' 

 of our neck, and ' a few gray tubercles ' in our 

 lungs/' 



Other pathologists, among them Lord Lister 

 and Profs. Bang, Nocard, and Sims Woodhead, 

 refused to accept Dr. Koch's statements as con- 

 clusive, and \vhile they admit that the danger 

 from tuberculous milk and meat may have been 

 much overrated, they strongly deprecate any re- 

 laxation of the present laws against tuberculous 

 cattle and their products. 



A royal commission was appointed by the Brit- 

 ish Government, soon after the congress, to deter- 

 mine the exact relation between the two dis- 

 eases. 



Bats and the Plague. It had long been sus- 

 pected, owing to the fact that a rat plague was 

 almost invariably observed to precede and accom- 

 pany human epidemics, that there was some con- 

 nection between rats and human plague. So that 

 when, in 1894, Yersin and Kitasato isolated the 

 plague bacillus (Bacillus pestis), and it was sub- 

 sequently found in rats, the identity of the two 

 diseases was accepted with little question. These 

 and other investigators worked out the relation- 

 ship between the two diseases, and a series of sani- 

 tary regulations are now in force at many sea- 

 ports liable to plague infection which have for 

 their chief purpose the destruction of infected 

 rats. The local government board of London 

 issued, in the past summer, a series of recom- 

 mendations to the British port authorities for 

 prevention of the plague, which consisted almost 

 entirely of directions for destroying infected rats. 

 In the London Lancet for Aug. 3, 1901, Dr. Alex- 

 ander Kdington, director of the Bacteriological 

 Institute of Cape Colony, published an article in 

 which he described experiments made during an 

 epidemic of plague in Cape Town which at any 

 rate suggest the possibility that rat plague and 

 human plague are not the same disease, and are 

 due to different bacilli. His researches, however, 

 were not extensive, and do not justify any change 

 in present preventive measures. 



METALLURGY. Structure of Metals. 

 Much attention has been paid of late years to the 

 study of the structure of metals as afi'ecting their 



qualities in use, and in this great aid has been 

 afforded by micrographical examination. 



A research concerning which a first paper was 

 read before the Iron and Steel Institute has been 

 carried on for six years by Prof. J. O. Arnold, for 

 the purpose of elucidating the cause of the ex- 

 traordinary discrepancies w 7 hich are met with in 

 the practical working of two steels, perhaps of 

 identical composition, contradicting what might 

 have been anticipated from the results of previous 

 experiments. A series of specimens of metal con- 

 taining iron and from 0.00 to 1.95 per cent, of 

 carbon, and practically free from silicon, man- 

 ganese, sulfur, and phosphorus, were experimented 

 upon to ascertain the various effects produced 

 by the usual forms of heat and mechanical treat- 

 ment to which metals are liable to be subjected. 

 Seventeen types of metal were experimented upon, 

 each of which was cast in a composite mold with 

 a central head, so as to obtain four bars at the 

 same time with the same pot of metal. The bars, 

 which were of course identical, were broken off' 

 at the head; two of them were tested as cast, 

 while the other two were rigorously annealed 

 and tested, records being taken of the influence of 

 annealing upon their properties and structure. 

 The results attest the enormous difficulty with 

 which the elucidation of the behavior of the sim- 

 plest form of steel is attended. A careful inves- 

 tigation of the specific gravities gave negative re- 

 sults, and showed that no correlation exists be- 

 tween the density and the mechanical properties 

 of castings. As in specimens which were com- 

 pared with one another, the composition and an- 

 nealing conditions were identical; there was only 

 one condition which could have had a variable in- 

 fluence, viz., the initial temperature of the cast- 

 ing. This might determine a condition of metal 

 which might survive the drastic operation of an- 

 nealing. This suggestion was offered as a pos- 

 sible explanation, but actual proof awaits the dis- 

 covery of a means of accurately determining the 

 temperature of molten steel. The author spoke 

 of the hopelessness of generalizing laboratory re- 

 sults obtained with small plain bars and putting 

 forward the generalizations for guidance in works 

 practise. As a practical summary of the les- 

 sons taught by these preliminary results, Mr. Ar- 

 nold affirms that steel consisting of pure iron 

 and carbon is not a suitable material for fulfilling 

 the modern specifications drafted by engineers for 

 steel castings; that the ductility demanded can 

 be insured with ease, but not the required tenacity ; 

 that the tenacity can be obtained, but with the 

 almost complete loss of ductility; and with the 

 exception of the nearly pure iron, the castings he 

 had described that is, without silicon or man- 

 ganese have small manufacturing value. Never- 

 theless, they form the basis on which the me- 

 chanical influence of silicon and iron can alone be 

 scientifically measured. 



In another paper relating to this subject, on 

 Practical Problems in the Metallography of Steel, 

 Mr. Arnold said that the theory that -steels of 

 identical chemical composition would necessarily 

 have the same mechanical properties had long 

 since been discarded. It is a fact that steel of ex- 

 cellent chemical composition, giving highly satis- 

 factory mechanical tests, may nevertheless utterly 

 fail in use; thus, a ductile steel which bends 

 double cold Without any sign of flaw or failure 

 may, under the influence of vibration, snap like 

 a piece of glass, though only subjected to me- 

 chanical stresses well below its elastic limit. This 

 is proved beyond all doubt by data in the author's 

 possession. In many cases the microscope is 

 capable of giving warning of the dangerous char- 



