8 LABORATORY EQUIPMENT. 



of the sun be prevented from striking one's desk. Strong sunlight may 

 weaken or even destroy the virulence of cultures, or bring about many 

 changes in sera. Even diffuse daylight should not be considered as entirely 

 inert. A general rule to be remembered is never to expose any biological 

 reagent, be it a bacterial culture or any form of its derivative, a serum, or 

 any other substance to daylight any longer than is absolutely necessary. 

 If this dictum is followed, one will avoid many a difficulty. 



To conform with this idea, it is wise to have upon the table a small closet into which 

 the cultures and sera can be placed for the time that they are being used. Such a con- 

 venient receptacle can be made out of a large cigar box, painted black inside and out, 

 with its lid replaced by a small black curtain. 



The table or desk at which one works should be near the window, and covered with 

 filter-paper, upon which should come a glass or asbestos plate. Instead of a wooden 

 table it is certainly more elegant, but costlier to have a top plate of glass. Upon the 

 table there should be a Bunsen burner, a microscope, a lamp for microscopic work at 

 night, a dish filled with sublimate or cresol into which the infected substances, old 

 cultures, used pipettes and graduates are placed. 



It is very convenient to have running water and a hood in the same room. Still 

 neither of these is absolutely necessary. As for larger apparatus must be mentioned, 



a thermostat, a mechanism for shaking, a dry 

 sterilizer, a good autoclave, a water-bath, an in- 

 strument sterilizer, a water or electrical centrifuge, 

 an ice chest, a closet for instruments and glass- 

 ware, and finally animal cages of the kind that are 

 easily cleansed. 



As for instruments and glassware the following 

 are required: scalpels, scissors, forceps, glass- 

 cutter, sterilizable syringes of various sizes, grad- 

 uates of 10, 25, 100, and loooc. cm. capacity each, 

 pipettes of i c. cm. with i/ioo divisions and pipettes 

 of 10 c. cm. with i/io divisions, a sterilizable 

 FIG. 2. Instrument (After Czap- pipette retainer, Erlenmeyer flasks, Petri and 

 Standardization f Kolle's dishes, test-tubes, dark glass flasks, ordinary 

 water glasses, funnels, glass tubes of various sizes, 

 and test-tube racks. Furthermore, a platinum needle and a platinum loop are required. 

 For making a loop of a definite size, and one which can always be referred to, the small 

 instrument devised by Czaplewski is of great help. It consists of four round metal bars 

 of i, 2, 3, and 5 mm. in diameter around which the platinum wire can be twisted in 

 order to make a standard loop (Fig. 2). 



All instruments and glassware used for serum work should be perfectly 

 clean. It is best to have all the glassware plugged with non-absorbent 

 cotton, and sterilized by dry heat. It is never advisable to clean the glass- 

 ware with strong acids, alkalies or other strong chemicals. If this has been 

 done, the chemicals must be thoroughly removed by washing, as the slightest 

 trace may interfere with the accuracy of some tests. 



All used glassware should at once be placed into a disinfecting solution. 



