204 



THE AMERICAN MONTHLY 



[November, 



use in the laboi-atory at Purdue Uni- 

 versity now three years is one which 

 was designed after the description, by 

 Mr. W. Bateson, of the bath in use 

 at Dr. Sedgwick's laboratory, at 

 Cambridge, England. This bath was 

 constructed by a tinsmith in the city 

 of Lafayette ; cost $4.00. It is an 

 oblong box 16 in. by 10 in. by 6 in. of 

 tin-lined copper, supported on four 

 legs, at a height of 11 in. from the 

 table. The portion beneath the box 

 is also enclosed so that the lamp flame 

 may burn undisturbed by current 

 through the door. The top of the box 

 is perforated with fifteen holes, some 

 of them two. others two and one-half, 

 inches in diameter. Copper disks 

 cover these holes tightly when not in 

 use. The vessels used in imbedding 

 are porcelain crucibles which fit the 

 holes closely and hang down into the 

 box, held only by the side of the cruci- 

 ble. An oven for drying slides is 

 placed on one side of the box : it is 

 four in. from the bottom, is four in. 

 deep, 8 in. long, and i^ in. high ; it 

 is shut in by a lid hinged to the side 

 of the box above the oven. There is 

 in the top of the box a small hole 

 with a collar for a cork to hold the ther- 

 mometer, and a second for heat reg- 

 ulator if desired. The water is never 

 allowed to reach the bottom of the 

 oven, and thus the oven and the cru- 

 cibles are surrounded by steam whose 

 temperature is determined by a ther- 

 mometer which dips down so as to 

 have its bulb on the level of the bot- 

 toms of the crucibles. The depth of 

 the bath allows the presence of a con- 

 siderable amount of water, and the 

 temperature of the bath is thus kept 

 very even indeed without the aid of 

 a regulator. We do not consider the 

 closed wells desirable, but prefer to 

 have the steam immediately surround 

 the imbedding dish. Porcelain cru- 

 cibles are desirable to use because so 

 easily cleaned, and because the white 

 color makes the object appear to stand 

 out very prominently. It is desirable 

 also to have the oven as near the level 

 of the crucibles as the construction of 



the bath w^ll permit, for the oven 

 should not be bathed in the water but. 

 only in steam, the temperature of 

 which is under control by help of the 

 thermometer. 



o 



The Bacterium of Swine-Plague. 



BY D. E. SALMON AXD THEOBALD 

 SMITH* 



The bacterium of swine-plague, as 

 it was observed in several outbreaks 

 in the east, may be quite easily found 

 in the spleen of animals which have 

 succumbed to the disease. Cover- 

 glass preparations of the spleen pulp, 

 stained in a solution of methyl violet 

 and mounted in xylol balsam, reveal 

 the presence of elongated ovals or true 

 bacteria, usually in pairs, and then 

 appearing like figures of eight. When 

 not too deeply stained, a narrow, well- 

 stained periphery, of nearly uniform 

 width, surrounds a paler, sometimes 

 nearly colorless, centre. The stained 

 border mav then be compared to the 

 line forming the figure of eight. The 

 bacterium is readily stained by other 

 anilin colors also. In such a prep- 

 aration the bacterium measures about 

 .0012 mm. to .0015 mm. in length, 

 and about .0006 mm. in width. In 

 the various culture media the bacteria 

 vary slightly both in size and form 

 from those observed in cover-glass 

 preparations of the spleen, being 

 smaller when multiplication is very 

 rapid, larger when it is I'etarded. 



It multiplies more readily in slightly 

 alkaline than in neutral media. It 

 grows readily in meat infusions, in 

 milk, on nutrient gelatin, agar-agar, 

 blood serum , and potato. When cul- 

 tivated in nutrient liquids it is motile^ 

 its movements being very vigorous 

 during the first and second days of 

 cultivation. Later a whitish ring forms 

 around the glass at the surface of the 

 liquid, which, in advanced cultures, 

 sometimes becomes a more or less 

 complete membrane. In milk it mul- 

 tiplies without producing any change 

 distinguishable by the naked eye. tn 



* Read before A. A. A. S., Aug 



