494 



SCIENCE 



[N. S. Vol. XXXIV. No. 876 



here the advantages of these methods are most 

 clearly brought out. The third chapter gives 

 a statement of the Hertzian form of Maxwell's 

 equations. In Chapter IV. Hertz's theory for 

 moving media is discussed and it is shown 

 how experimental results prove its inade- 

 quacy. 



The motion of a single charge moving with 

 uniform velocity through the ether is consid- 

 ered in Chapter V., and in the next chapter 

 the electron theory of Lorentz is applied to 

 stationary media. The treatment of stresses 

 within a material medium is not satisfactory; 

 no account is taken of the variation of specific 

 inductive capacity with the state of strain, 

 and therefore the stress system obtained is 

 that of Maxwell, which we know is not capable 

 of experimental verification. In the last chap- 

 ter Lorentz's theory is applied to moving 

 bodies, ending with a brief account of aberra- 

 tion. The interpretation of the Lorentz 

 transformation in terms of the theory of 

 relativity is not touched upon. 



There are many other matters that might 

 properly come within the scope of this work, 

 but it does not profess to be exhaustive, and 

 as an outline it may be commended most 

 highly. 



E. P. Adams 



CONTAGIOUS ABOSTION IN CATTLE 

 It is often asserted that tuberculosis is, 

 from the economic point of view, the most 

 important disease affecting the cattle of this 

 country. It is undoubtedly true that con- 

 tagious abortion is to be ranked as second in 

 economic importance and, by many of the 

 best informed breeders and dairyman this 

 disease, that may destroy the usefulness of a 

 dairy animal during one fourth to one half of 

 the average period of productivity, is consid- 

 ered more important than tuberculosis. Cer- 

 tainly it is true that the breeder and dairy- 

 man have been more helpless in the fight 

 against this disease than against tuberculosis, 

 for knowledge is available that will enable 

 any farmer to free his herd from tubercu- 

 losis and so to maintain it. In the case of 

 contagious abortion, no such knowledge is 



available, and until quite recently no method 

 had been devised by which it could be ascer- 

 tained whether or not an animal about to be 

 introduced into a healthy herd was infected. 

 The work of Bang and his associates has 

 demonstrated the cause of the disease as it 

 appears in Denmark. This work has been 

 confirmed by others in England and Ger- 

 many. In the United States, in spite of the 

 efforts of many investigators, the B. abortus 

 of Bang had not been found. Dr. W. J. Mac- 

 Neal, formerly at the University of Illinois, 

 isolated an organism that he believed, rely- 

 ing on its cultural and morphological charac- 

 teristics, to be identical with the Bang organ- 

 ism. 



Within the last year, the complement devia- 

 tion test, now so widely used for the diagnosis 

 of syphilis, has been applied with great suc- 

 cess to the detection of contagious abortion 

 in cattle, by Drs. Bang and Holth in Copen- 

 hagen. Dr. W. P. Larson, who had become 

 familiar with the test during his association 

 with the Danish bacteriologists, returned to 

 this country in May, since which time he has 

 been engaged in connection with the depart- 

 ments of agricultural bacteriology and veteri- 

 nary science of this experiment station in the 

 study of the disease in this country. Using 

 a culture of the organism brought from 

 abroad as one of the specific components of 

 the test, it has been shown that the disease as 

 it occurs in this country is caused by the 

 same organisms as found in Europe. Using 

 the blood serum of known infected animals, 

 the complement deviation test can be em- 

 ployed to identify a suspected organism. The 

 organism has been isolated from fetuses from 

 five herds in various parts of the state and the 

 identity of the cultures established by the 

 test. There remains no doubt that the disease 

 in this country is caused by the same organ- 

 ism as that found in Europe. 



H. L. EUSSELL, 



Director 



Agricultural Experiment Station, 

 Madison, Wis., 

 September 1, 1911 



