354 



SCIENCE 



[N. S. Vol. XLIV. No. 1132 



themselves, yet are capable of transmitting it 

 to others. The virus has also been found in 

 the alimentary tract of patients and experi- 

 mental animals with infantile paralysis, a fact 

 which may explain why it is that a gastroin- 

 testinal upset sometimes precedes and appears 

 to be the cause of an attack of infantile paraly- 

 sis. The virus has been proved to reach the 

 patient's central nervous system, in which its 

 main pathological action is exerted, by travel- 

 ling along peripheral nerves — the sciatic, the 

 nasal nerves, the optic nerves and tracts, for 

 example — to the spinal cord or brain as the 

 case may be, and this is to be regarded as the 

 normal mode of infection in poliomyelitis; 

 gross infection of the blood stream with the 

 virus may also suffice to infect the brain. Evi- 

 dence has been adduced to show that certain 

 flies, particularly Stomoxys calcitrans, the 

 common stable fly, may act as carriers of the 

 disease. In addition the virus has been found 

 on clothes, handkerchiefs and toys used by pa- 

 tients in the acute stages of infantile paraly- 

 sis. The careful examination of washings 

 from the mouth or intestine have shown that 

 human beings may remain carriers of the virus 

 for as long as six months. According to 

 FJing, quarantine for infantile paralysis 

 should last at least a fortnight — in New York 

 it now lasts for ten days or thereabouts, we are 

 told — though it is clear that no certainty at- 

 taches to any fixed period in this connection. 

 There is reason to believe that the great ma- 

 jority of adults and many children may be in- 

 fected with the virus without being a penny 

 the worse for it, either because the virus is en- 

 feebled or because the resistance of such in- 

 dividuals is high. Thus it is probable that 

 every patient actually ill with the disease has 

 in his immediate environment a number of 

 mild and abortive cases of infantile paralysis 

 that escape observation or detection and diag- 

 nosis, and also a still larger number of per- 

 fectly healthy people who are all carriers of the 

 infecting agent and therefore potential sources 

 of infection to others. It would seem as if all 

 these persons developed a relatively high de- 

 gree of immunity to the virus, a fact which 

 may explain the comparative immunity of 

 European towns or villages visited by epi- 



demics of infantile paralysis to the occurrence 

 of further epidemics during the next few 

 years. In fact, as with cerebrospinal menin- 

 gitis, the number of the carriers of the infec- 

 tion may be much larger in infantile paralysis 

 than the number of the victims of an epidemic 

 of that disease. — The British Medical Journal. 



NOTES ON METEOROLOGY AND 

 CLIMATOLOGY 



THUNDERSTORMS OF THE UNITED STATES 



A thorough study of the distribution of 

 thunderstorms has been made by Mr. W. H. 

 Alexander with the aid of the officials in 

 charge of more than one hundred of the reg- 

 ular weather bureau stations. 1 Following this, 

 Professor R. DeC. Ward has fittingly brought 

 out the significance of the thunderstorm as a 

 climatic phenomenon. 3 



Thunderstorms are produced (1) by the ex- 

 cessive heating of the lower air; (2) by the 

 over- and under-running of winds of different 

 temperatures, which in some way cause moist 

 air masses to rise rapidly; and (3) by the cool- 

 ing of the upper air. These causes usually are 

 not individually responsible for any thunder- 

 storm; but act in conjunction. 3 Excessive 

 heating of the lower air occurs in summer and 

 most favorably on plains, plateaus and inter- 

 mont basins. Thus in the United States the 

 maximum number of thunderstorms is to be 

 expected in the Mississippi Valley, and in the 

 western mountain and plateau region. Fur- 

 thermore, most come in summer : in 126 of 139 

 stations considered 4 the month with most 

 thunderstorms is June, July or August. Cy- 

 clonic activity in a region subject to marked 

 temperature changes is usually responsible for 

 the production of thunderstorms by over-run- 



i Mo. Weather Bev., July, 1915, pp. 324-340, 13 

 maps. 



- Pan-American Scientific Congress ; abstract in 

 Mo. Weather Rev., December, 1915, p. 612. 



3 A comprehensive investigation of the physics 

 of the thunderstorm was published in 1914 by 

 Professor W. J. Humphreys. See review in Sci- 

 ence, December 4, 1914, p. 823. 



^ H. Lyman, ' ' Percentage Frequency of Thun- 

 derstorms in the United States," Mo. Weather 

 Kev., December, 1915, pp. 619-620. 



