SCIENCE. 



[Vol. XVII. No 421 



pounds of powder wUl be used. The shell will contain from 300 

 to 400 pounds of nitro-glycerine, enough to blow up any vessel 

 afloat if struck right. The muzzle of the gun will protrude for 

 ten feet under water, and the projectile will be carried from 750 

 to 1,000 feet. The projectile will extend eight feet beyond the 

 muzzle of the gun before firing. We intend to try the gun for 

 the first time at Newport next July, having obtained from Con- 

 gress an appropriation for making the tests. 



"With a few such vessels as the 'Destroyer' will be when 

 equipped with our gun, the armed fleets of the world could be 

 swept out of existence. I believe that this invention will revolu- 

 tionize naval gunnery throughout the world. One of our shells 

 •can be sent right through the netting and into the side of a vessel, 

 where a torpedo could not penetrate. Commodore Folger of the 

 Ordnance Department has written a letter to me, saying that he 

 has prepared a heavy steel netting for a target, upon which our 

 gun can be tested. Later we shall buy an old hulk and blow it 

 up with one of our percussion shells, to show the eflacacy of the 

 new gun. 



"I think that if the test proves satisfactory the government will 

 arm some of the naval vessels with it. For the price that one of 

 our big new ships would cost we could build and arm five of the 

 smaller ships, which would be able to sink the best navy afloat. 

 If the nations should arm their navies with these guns, it would so 

 ■enhance their destructive power that the powers would not dare 

 to go to war with each other. Since ships have been armed with 

 the Hotchkiss rapid-firing guns, there has not been a naval battle. 

 In a sea fight these guns would cause terrible havoc. Vessels of the 

 ^Destroyer' type are to be heavily armored, so that they can ap- 

 proach any vessel without being injured. These vessels will be 

 ■only a foot out of the water, and that part will be armored, so very 

 little will be exposed to an enemy's guns. One of these vessels, 

 made to steam at great speed, can be made very effective." 



Mr. Bushnell was associated with Ericsson in the construction 

 of the '■ Monitor." 



HEALTH MATTERS. 



African Arrow Poison. 



The poisons used by the natives of Africa to render fatal the 

 wounds made with their arrows, as described by Mr. Stanley in 

 Ills recent work on Africa, are, when fresh, of most extraordinary 

 power. Faintness, palpitation of the heart, nausea, pallor, and 

 beads of perspiration break out over the body with extraordinary 

 promptness, and death ensues. One man is said to have died within 

 one minute from a mere pin-hole puncture in the right arm and 

 right breast; another man died within an hour and a quarter after 

 being shot; a woman died during the time that she was carried a 

 distance of a hundred paces; others died in varying spaces of 

 time up to a hundred hours. The activity of the poison seemed 

 to depend on its freshness. The treatment adopted, as we learn 

 from the Medical and Surgical Reporter, was to administer an 

 «metic, to suck the wound, syringe it, and inject a strong solution 

 of carbonate of ammonia. This carbonate-of-ammonia injection 

 seems to have proved a wonderful antidote, if it could be adminis- 

 tered promptly enough. One of the poisons with which the 

 weapons are smeared is a dark substance like pitch. According 

 to the native women, it is prepared from a local species of arum. 

 Its smell when fresh recalls the old blister plaster. It is strong 

 enough to kill elephants. This poison is not permitted to be pre- 

 pared in the village. It is manufactured and smeared on the 

 arrows in the bush. These results of the African arrow poison 

 are quite remarkable; but it would be interesting to know if they 

 owe any thing to fear and its effects, or if similar results can be 

 ■obtained by inoculating the lower animals. 



Inoculation of Dog Serum as a Remedy for Tuberculosis. 



In a series of communications made in the course of the last 

 two years to the Societe de Biologic, MM. Hericourt and Richet 

 have given the results obtained by the injection of the blood of an 

 animal refractory to tuberculosis, such as the dog, into the 

 economy of one susceptible to the onslaughts of the bacillus. They 

 have demonstrated experimentally, according to the Lancet, that 

 such a proceeding exerts a retarding influence on the evolution 



of tuberculosis artificially communicated, without, however, stop- 

 ping it altogether. With a view of intensifying these partially 

 protective properties of canine blood, they inoculated the dog with 

 a large dose of very active tuberculous matter, and one month 

 later (the animal having lost flesh, and exhibiting manifest signs 

 of ill health) injected into the peritoneal cavity of three rabbits 

 seventy cubic centimetres of the dog's blood. A week later these 

 rabbits were, with three other test-rabbits, inoculated with strong 

 tuberculous virus, with the result that in twenty-five days two of 

 the latter had succumbed, the rest surviving. Their ultimate fate 

 is not recorded. Encouraged by these results, MM. Hericourt 

 and Richet have extended the application of their method to 

 tuberculous human beings, employing the serum only, and select- 

 ing the interscapular region as the seat of inoculation. M. Richet 

 reports (Socigte de Biologie, Jan. 24) that four phthisical men 

 have, since the early part of December, 1890, been subjected to 

 this novel treatment. The results obtained seem to warrant the 

 assumption that the introduction of the serum of dog's blood into 

 the human economy counteracts, to some extent at least, the 

 noxious influence of Koch's bacillus. 



LETTERS TO THE EDITOR. 



*#* Correspondents are requested to be as brief as possible. The toriter^s name 

 is in all cases required as proof of good faith. 



The editor mill be glad to publish any queries consonant with the character 

 of the journal. 



On request, twenty copies of the number containing his communication will 

 be furnished free to any correspondent. ' 



Can One see the Blood-Corpuscles in his own Eyes ? 



To some this may seem an idle question, — an absurdity; but 

 when we remember that the sensitive layer of the retina is on 

 the back side, and that there are blood-vessels in front of it, it 

 may not seem so improbable. Nevertheless, the ease with which 

 it may really be done is quite surprising. 



If the eyes are turned toward a dimly lighted blank space, and 

 adjusted to see distant objects, or as when we " gaze on vacancy," 

 there wiU appear flitting across the illuminated area small bright 

 spots. They will seem to flash into vision, pass over a few de- 

 grees, usually in a curved path, then suddenly disappear. The 

 circumstances found favorable for observing this phenomenon are 

 to look toward the sky or a snowy surface on a cloudy day, or on 

 a brighter day with the eyes nearly closed. Seldom more than a 

 dozen of these luminous points may be seen at once, and usually 

 not more than two or three distinctly. 



They may be easily distinguished from the tear-drops trickling 

 over the front of the eye, which are often visible at nearly the 

 same time, by their being of uniform size, and moving rapidly in 

 different directions ; while the tears are of variable size, like rain- 

 drops on a window-pane, and rnove slowly downward, or by the 

 motion of the eyelids upward. 



They are not to be confounded with muscce volitantes, which 

 are of variable shape, size, and color, and, besides, slow of motion, 

 and not so quickly disappearing. 



That these minute bodies are really red corpuscles floating 

 through the retinal capillaries, is indicated by the following 

 facts : — 



1. They move in definite paths. Having noted one, another 

 will be seen to pass exactly the same path in from half a second 

 to two seconds. 



2. They always move in the same direction in the same path, 

 never back and forth. 



3. They are of uniform size, and appear to be of a yellowish 

 color. 



4. By comparing them with objects of known size at known 

 distances, they have been approximately estimated to correspond 

 in size to red corpuscles. Accurate measurements seem im- 

 practicable from the nature of the case. 



The reason that they are visible whfle the capillaries in which 

 they float are not, is easily explained by the familiar principle that 

 we become insensible to that which is constantly present, and are 

 specially impressed by that which is transient or novel. The 

 familiar experiment of Purkihje shows us that the capillaries 

 may become visible when light comes from a novel direction, so 



