CHAPTER XXXVII. 551 



1036. Precautions to Insure Complete Sterilisation oJ Apparatus.- 



It cannot be too strongly emphasised that the utmost precautions 

 must be taken to insure complete sterility of all apparatus. 

 Bacterial infections of the cultures are fatal. The worker who 

 is not familiar with the minute precautions taken by surgeons 

 and bacteriologists in sterilising instruments, apparatus, etc., is 

 advised to become so before undertaking tissue-culture work. A 

 rigid asepsis is necessary for the preparation of any tissue-culture. 

 These words are addressed especially to the zoologist who may 

 undertake tissue-culture work ; dirty floors and benches, dirty walls 

 and garments, and casual methods will all contribute towards 

 failure. A clean, warm room should be set aside for making the 

 cultures, another for making the various plasmas, and, if possible, 

 another for incubators and incubator microscopes. The ordinary 

 zoological or botanical laboratory is generally unsuitable for such 

 delicate work. 



Dr. Drew informs me that whether in vitro culture be carried out 

 in a special laboratory or not, it is advantageous to use a specially 

 constructed glass chamber to shield the cultures from chance con- 

 tamination. Such a chamber is supplied by Hearson's ( 11), or 

 can be made by any carpenter. The apparatus consists essentially 

 of a glass box in a wooden or metal framework measuring about 

 2 feet 6 inches in length, 2 feet in width, and about 1 foot in height. 

 The top is hinged so as to allow ready access to the interior for 

 cleaning, etc. The side facing the worker is made of wood, with 

 either two small wooden doors or a piece of thick sheet rubber 

 pierced so as to allow the easy entrance of the hands. The box 

 should have glass racks to contain the hollow ground slides and a 

 glass table for the cover-glasses. The slides are cleaned and stored 

 in absolute alcohol ; they are removed from this by means of forceps 

 and are flamed in a Bunsen and quickly transferred to the glass 

 racks ; cover-glasses are cleaned in acid bichromate, washed in 

 water till free from all trace of the acid, rinsed in distilled water, 

 then in absolute alcohol, and stored in ether. They are removed by 

 means of forceps and flamed and placed on the previously sterilised 

 glass table. Here both slides and cover-glasses are protected from 

 all falling dust, and can be manipulated easily with the hands 

 through the openings in the case. The majority of failures occur 

 through infection taking place, and the glass chamber reduces such 

 a possibility very greatly. 



1037. Simple Culture Technique by means of Frog Lymph (HARRI- 

 SON, op. cit., 1907). Pieces of embryonic tissues of frog embryos 



