430 



SCIENCE. 



[Vol. II., No. 34. 



starch and iodide test is so dependent upon 

 other elements than the simple presence of 

 ozone, that it is not thoroughly reliable. It is 

 also open to the error of reacting to substances 

 other than ozone. Still, admitting the state- 

 ment that there is more nascent ozone at high 

 elevations, the explanation of its action in the 

 cure of phthisis is still to be sought. Some 

 rather visionar}- theorists, as it seems to the 

 writer, claim that it liuds a direct admission 

 to thetliseased siDOts in the lungs, and, by its 

 poorer oxidizing, it burns up in loco the mor- 

 bid products. 



We should rather attribute its influence to the 

 fact, that, where ozone exists free, there is no 

 decomposing matter to be oxidized. It seems 

 to us to be indicative of the existence of pure 

 air, rather than a direct agent in destroying 

 the morbid products in the lungs. 



4. Immunity from phthisis. — Another ar- 

 gument in favor of elevation in the cure of 

 phthisis is, that at certain heights there exists 

 an immunity from the disease. The disease 

 is not endemic at siich elevations. 



This is in the nature of negative evidence ; 

 but it is certainlj' valuable as an element of 

 prophylaxis, and we think that it can be ap- 

 plied as an argument in favor of cure. Ruehle 

 (op. cit.) says, "A height of at least 1,800 or 

 2,000 feet seems to be requisite for this pur- 

 pose. Phthisis is rare on the Hartz, Styrian 

 (iu Purzgau), and Swiss mountains." Jac- 

 coud (Flint's Practice of medicine, p. 296) 

 " states that the observations for fifteen con- 

 secutive j-ears warrants him in asserting, that, 

 in Alpine situations elevated 4,000 feet, tuber- 

 culosis is unknown ; and especially is this true 

 of villages at an elevation of 5,500 feet." 

 Dr. Irwin reports for Fort Defiance (6,500 

 feet), north-western New Mexico, "During a 

 service of some seven years in ISTew Mexico 

 and Arizona, I never saw or heard of a case 

 of tuberculous disease amongst the native in- 

 habitants of those territories." And Dr. 

 Denison, in his work entitled ' Rocky Moun- 

 tain health resorts,' writes, "After having 

 quite thoroughly canvassed the subject among 

 physicians of Colorado, I place the altitude of 

 approximate immunity of this state at 6,000 

 feet." 



Taking a mean of all these quotations, we 

 may safely assert, that, broadly speaking, an 

 altitude of from 5,000 to 6,000 feet affords an 

 approximate immunity from this disease. 



5. An aseptic atmosphere. — Lastly, we will 

 speak of the influence of elevation iu the 

 cure of phthisis in producing an aseptic at- 

 mosphere. In these days of germ-theories 



and of Koch's experiments, we cannot but 

 give emphasis to this element of antisepsis as 

 an element of prophylaxis and cure of phthisis. 

 Professor Tyndall's experiments show the 

 abundance of germs floating in the air at sea- 

 level, and an entire absence of such germs at 

 the altitude of the 'Belle Alp' hotel (7,000 

 feet) . Whether a lower elevation will furnish 

 this aseptic atmosphere has not been proven 

 experimentally ; but it would seem to be rea- 

 sonable to argue that an elevation correspond- 

 ing to that of immunity from phthisis would 

 furnish such an atmosphei'e. 



Bisume. — There are other elements, such 

 as humiditj' of the air, temperature, precipi- 

 tation, etc., more or less dependent upon ele- 

 vation, which we shall have occasion to speak 

 of more at length. But, to make a risumv of 

 our study to this point, we can say that a rise 

 in elevation increases the heart-beat and the 

 rapidity of the circulation, therebj- hastening 

 the absorption of the morbid products in phthi- 

 sis, and increasing the metamorphosis of tissue, 

 and hence the vital force ; that it likewise 

 produces greater depth of respirations, and a 

 more health}- action of the diseased portions 

 of the lungs ; that it gives a purer air, and 

 affords an approximate immunity from the 

 disease ; and, finally, that it affords an asep- 

 tic atmosphere, in which the Bacillus tubercu- 

 losis does not exist. The extent of elevation 

 desirable for the production of this effect can 

 be stated to be at least 5,000 feet. 



Having arrived at these conclusions, it re- 

 mains for us to apply them to our subject. 

 B3- consulting table I., columns i. and ii., it will 

 be seen, that, of all the resorts for the cure of 

 phthisis in this country', the eastern slopes of 

 the Eockj" Mountains alone furnished the de- 

 ■ sirable elevation. The distance between Den- 

 ver and Santa Fe is in the neighborhood of 

 375 miles in extent. Throughout this whole 

 extent, pleasant locations for invalids are to be 

 found at elevations varying from 5,000 to 

 6,000 feet. 



( To he continued.) 



HISTOLOGY OF INSECTS. 



Inspired by Weissmann's well-known researches 

 on tlie post-embryonic development of insects, Vial- 

 lanes has studied the structure and changes of 

 rarious tissues, principally in Musca vomitoria, but 

 also in other insects during their metamorphoses. 

 His results occupy nearly an entire volume,' and 

 make an important addition to knowledge, the more 

 welcome because the author deals chiefly witli tliose 

 tissues which have heretofore been least worked 

 ^ Vol. xiv. ser. vi. of Add. sc. nat., zool. 



