186 



THE AMEEICAN MONTHLY 



[October, 



Though we must regard as an ex- 

 cellent addition in the study of bacte- 

 ria the more rigorous technique of 

 the present method of solid substrata, 

 especially in .its applicatioii to the 

 isolation of different forms, it can 

 never supplant liquid cultures, and 

 therefore any apparatus which will 

 inaterially simplify the laborious and 

 minute technique and reduce to a 

 minimum the sources of error con- 

 nected with the study of microscopic 

 fungi in liquid media must be hailed 

 as an important and lasting step in 

 advance. The culture-tube devised 

 by Dr. D. E. Salmon has certainly 

 proved to be such. Though in con- 

 stant use for over a year is his labora- 

 tory. Dr. Salmon has not yet found 

 the opportunity of publishing an ac- 

 count of it, and owing to the pressure 

 of official duties his appearance at this 

 ineeting is impossible. I shall, there- 

 fore, take the liberty of pointing out, 

 in the briefest manner, the construc- 

 tion and use of the culture-tube, w^ith 

 the hope that he will present a more 

 extended description at a later date. 



The culture-tube consists of a test- 

 tube-like body or reservoir, of rather 

 heavy glass, about 4 to 5 inches in 

 length and three-fourths of an inch in 

 internal diameter. Over the top of 

 this reservoir a second hollow piece 

 is fitted, which might be called a cap. 

 Its internal surface is ground to fit 

 snugly over the ground external sur- 

 face of the upper end of the reservoir, 

 thus forming a gi^ound-joint union. 

 This cap, abont 2^ inches long, ab- 

 ruptly contracts near its middle into 

 a narrow tube with an internal diam- 

 eter of about § of an inch. The third 

 piece, which might be called the ven- 

 tilating tube, is shaped like an in- 

 verted u, one limb being about 3 

 inches long, and i^ inches longer 

 than the limb which fits by means of 

 a ground joint over the narrow tube 

 of the cap. The longer, free limb of 

 the ventilating tube lodges a plug of 

 glass-wool from i^ to 2 inches long. 

 The limbs of the ventilating-tube are 

 about one inch apart. 



The culture-liquid is introduced by 

 removing the cap, which brings with 

 it the ventilating-tube, and it is steril- 

 ised in the tube. The liquid is inoc- 

 ulated by removing the ventilating 

 tube only. To prevent the ground 

 joints from sticking too firmly, a little 

 sublimated vaseline is introduced be- 

 tween the surfaces of the joint. 



The pipette, used to introduce a 

 drop of fluid containing bacteria, con- 

 sists of an ordinary glass tube about 

 ^ of an inch in diaineter and 2 to 3 

 inches long, one end of which is drawn 

 out into a very fine, almost capillary 

 tube, which must be long enough to 

 easily reach the bottom of the reser- 

 voir when introduced through the 

 narrow tube of the cap. A plug of 

 glass-wool occupies the other end, 

 which is closed by a rubber ball. 



The method of inoculating the cul- 

 ture-liquid is briefly as follows : — 



The pipette is first thoroughly ster- 

 ilised by flaming every poition of it 

 from the tip of the capillary tube to 

 near the rubber bulb until the con- 

 tained air is subjected to a tempera- 

 ture of at least 150° c. We usually 

 bring it to a dull red heat, avoiding 

 the contingency of melting the capil- 

 lary tube. It is hung with the rub- 

 ber bulb up to avoid its capillary 

 portion coining in contact with any- 

 thing while cooling. When suffi- 

 ciently cool the capillary portion is 

 again drawn once or twice through 

 the flame to destroy any particles that 

 may have become attached mean- 

 while. The ventilator of the culture- 

 tube, containing the bacteria to be 

 sown, is flamed and removed and the 

 naiTow tube of the cap flamed, the rub- 

 ber bulb slightly compressed, and the 

 pipette introduced, a few drops drawn 

 up, the pipette slowly withdrawn, the 

 cap flamed again, and the ventilator 

 replaced. The cap of the fresh tube is 

 now flamed before and after removing 

 the ventilator, the pipette introduced, 

 a drop allowed to fall into the culture- 

 liquid, the pipette removed, the nar- 

 row tube of the cap again flamed, and 

 the ventilator replaced. This is the 



