4i6 



SCIE'NCE. 



[Vol. XIV. No. 359 



but a single insect, and the commissioners were very solicitous 

 and also sceptical as to its ability to rapidly destroy the red scale. 

 Furthermore, they questioned whether the chalcid would destroy 

 the true red scale, as they did not believe that the scale on the or- 

 chards mentioned was identical with that about Orange. The 

 Vedalia has brought the people a simple, rapid, and effective 

 remedy for the white scale, and the commission was very solicitous 

 lest the people should give up the use of washes for the red scale, 

 and wait for the spread of the chalcid parasite. If the parasite 

 should multiply but slowly, which seems probable, the red scale 

 would be enabled to spread and do great harm before overtaken. 

 It is of the highest importance, at this time, that a constant fight 

 against this scale should be made ; and there should be no halting, 

 even if imperfect means of holding the pest in check are only at 

 hand. 



Professor Henry carefully examined the experiments conducted 

 by Mr. Coquillett with resin washes, and considers that he has used 

 excellent judgment in the manner in which he has conducted them, 

 and thinks he plans his spraying experiments carefully and with 

 good judgment, and carries them through with thoroughness to the 

 end. 



It seems of the highest importance that experiments with washes 

 be prosecuted, and that the great advance of the last year be fol- 

 lowed up vigorously. With the resin washes for the red scale, and 

 the Vedalia for the white scale, the citrus industry will again 

 move forward, and people have the confidence in it of former days. 



CAUSATION OF HOG-CHOLERA. 



Investigations of the epizootic diseases of swine, occurring in 

 the neighborhood of Baltimore, have been made by Professor Wil- 

 liam H. Welch, M.D., with the co-operation of A. W. Clement, 

 V.S., and F. L. Russell, V.S., in the Pathological Laboratory of 

 the Johns Hopkins University during the past two years. They 

 examined about fifty hogs, from six herds, affected with hog- 

 cholera, as well as several isolated cases. Only a summary of the 

 most important results will be given here, a fuller report being in 

 preparation for the volume of studies from the Pathological Lab- 

 oratory, to be issued by the Johns Hopkins Hospital. 



The most common and characteristic lesions, as given in the 

 Johns Hopkins Sulletiti for December, consisted in superficial and 

 deep necroses, either circumscribed or diffuse, of the inflamed 

 mucous and other coats of the large intestine, associated often with 

 superficial branny diphtheritic exudation. Similar necroses were 

 occasionally found in the stomach and small intestine, in the mouth, 

 palate, and epiglottis, and less frequently in the gall-bladder, bile- 

 ducts, and preputial sac. Some form of pneumonia was usually, 

 although not constantly, present. In a few cases pneumonia was 

 present without intestinal lesions ; more frequently intestinal le- 

 sions were observed with little or no pneumonia. Strongyles in 

 the bronchi were rarely missed. Bronchitis was the rule. Pleurisy 

 was common ; pericarditis and peritonitis were present in the 

 minority of cases. Redness of the skin was common, but incon- 

 stant. The subcutaneous, mediastinal, and abdominal lymph- 

 glands were usually swollen and reddened, chiefly in the periphery. 

 The spleen was often normal, but in many cases was moderately 

 and sometimes extremely swollen. The kidneys were either normal 

 or the seat of hemorrhages and of parenchymatous degeneration 

 or nephritis. The liver was often normal, but sometimes it pre- 

 sented necrotic areas. Ecchymoses were often observed in the 

 gastric and intestinal mucosa and beneath the epi- and endo- car- 

 dium. In some cases all of the organs of the body were studded 

 with small hemorrhages. 



The bacteriological examination consisted in the study of cover- 

 glass preparations from the different parts of the body ; in the in- 

 oculation of animals, either white mice or rabbits, with parts of the 

 lung, spleen, liver, intestine, and sometimes other organs ; and in 

 the preparation of Esmarch roll cultures, usually of agar, from the 

 blood, intestinal contents, and all of the principal organs of the 

 body. 



Of the bacteria isolated in pure culture and observed in micro- 

 scopical preparations of the tissues, only two species were suffi- 

 ciently common or had such distribution as to suggest an etiological 



relation to the disease. These are the so-called hog-cholera bacil- 

 lus and the swine-plague bacillus ; the former first described in the 

 " Report of the Bureau of Animal Industry for 1885 " as the bac- 

 terium of swine-plague, and in the report for 1886 as the bacterium 

 of hog-cholera, — a change of nomenclature due to the detection 

 in certain diseased swine in this country of the latter organism, 

 which now received the name of the " bacterium of swine-plague," 

 as it was believed to be identical with the micro-organism previ- 

 ously described by Liiffler and by Schiitz as the specific cause of 

 Schweine-Seuche in Germany. 



The bacilli of hog-cholera are short rods with rounded ends, 

 averaging I |U-2/; in length and about 0.6^ in breadth, but forms 

 both longer and shorter than these measurements may occur. 

 They are very actively motile. They grow readily on all of the 

 ordinary culture media, and best at temperatures between 30° and 

 38° C. They do not liquefy gelatine. The growth on gelatine and 

 on agar has a grayish or whitish color, often with a bluish trans- 

 lucence. Bouillon cultures present a diffuse cloudiness with 

 .whitish sediment and without surface membrane. The growth on 

 potato assumes generally a brownish or yellowish tint, but it may 

 be white, and sometimes is indistinct, although microscopically the 

 growth is abundant. The bacilli are killed by exposure for ten 

 minutes to a temperature of 58° C. In cover-glass preparations 

 from the fresh juices and tissues of animals dead of hog-cholera, 

 the bacilli stain readily, and for the most part uniformly, with ani- 

 line-oil gentian-violet. If the stained specimen be treated with 

 acetic acid, many of the bacilli appear with clear centre and stained 

 margin, which may be either uniform or slightly thicker at the 

 poles, as described in the reports of the Bureau of Animal Industry. 

 Some may present a typical polar staining, but they are not re- 

 garded as good polar staining bacilli, like those of swine-plague. 

 Various irregularities in staining appear in old cultures. 



The hog-cholera bacilli are pathogenic for rabbits, mice, guinea- 

 pigs, and pigeons. Only the experiments with rabbits will be de- 

 scribed here. These animals, when inoculated subcutaneously 

 with a platinum loop from a pure culture of hog-cholera bacilli, die 

 usually in from six to eight days, but the duration of life may be 

 shorter or longer. There is generally considerable dry purulent 

 infiltration at the seat of inoculation ; the subcutaneous lymphatic 

 glands on the same side are enlarged, and often present necrotic 

 foci ; the spleen is swollen, as a rule extremely, and of a dark red 

 color and firm consistence ; the liver generally presents yellowish- 

 white streaks and dots; the heart-muscle is fatty; and in some 

 cases ecchymoses, necrotic patches, and diphtheritic exudation may 

 be found in the intestinal mucosa. The bacilli, which often occur 

 in clumps, are found most abundantly at the seat of inoculation, in 

 the affected lymph-glands, ihe spleen, and the liver, and are often 

 so scanty in the blood as to escape detection by microscopical ex- 

 amination. The statements in the reports of the Bureau of Animal 

 Industry of the effects of these bacilli when inoculated in pigeons 

 have been confirmed by Professor Welch. 



The swine-plague bacilli are shorter than the hog-cholera bacilli. 

 Measuring on the average 0.8 to 1.4 fi in length, they may be very 

 small, and present the appearance of slightly oval bodies, more like 

 cocci than bacilli ; or, on the other hand, they may present them- 

 selves as rods of considerable length. In appearance and other 

 properties, they belong to the same group of organisms as the well- 

 known bacteria of chicken-cholera and of rabbit septicaemia. They 

 are devoid of independent motion. They grow on the ordinary 

 culture media, with the exception of potato, but at ordinary tem- 

 peratures the growth is less rapid and abundant than that of the 

 hog-cholera bacilli. They do not liquefy gelatine. On gelatine 

 and agar the growth is grayish, translucent, not extending far from 

 the point of inoculation. Bouillon cultures are sometimes diffusely 

 cloudy ; but more frequently the growth is in the form of a whitish, 

 rather viscid sediment, or in little specks, with clear fluid. When 

 planted on potato, there may be a feeble invisible growth for one 

 or two generations, probably due to the transferrence of a little 

 nutritive medium to the potato with the organisms. We have not 

 been able to cultivate them for several generations upon potato. 

 They are killed at a temperature slightly lower than that destruc- 

 tive to hog-cholera bacilli, and their vitality in cultures is much 

 shorter than that of hog-cholera bacilli. In cover-glass prepara- 



