EQUIPMENT AND PROCEDURES IN EXPERIMENTAL 



EMBRYOLOGY 



INTRODUCTION 



" Biologically Clean ." These are the two most frequently emphasized words in any 

 laboratory of experimental embryology, particularly during the initial stages of adjust- 

 ment. Glassware, instruments, solutions, and hands must be "biologically clean" before 

 any experimental results may be considered valid. The term means that, barring any ex- 

 perimental conditions Imposed, there is no possible contamination of living material 

 either by chemical substances, living parasites, or harmful organisms such as bacteria or 

 viruses. The conditions are such that any embryo, introduced into that environment, would 

 be expected to survive. The following precautions, in favor of biological cleanliness, 

 are suggested: 



1. Glassware : Eegardless of the source of the glassware to be used, it should be 

 thoroughly scrubbed with hot soap and water, and rinsed in running water for 

 at least 2 hours, rinsed with distilled water and air dried. If the glassware 

 Is cleaned with cleaning fluid {K. Bichromate and Sulphuric acid) it must be 

 thoroughly washed, and rinsed for a longer period (see Richards, 1956) because 

 the cleaning fluid is very adherent to glass. Properly cleaned glassware may 

 be wrapped in clean paper towelling and heat sterilized for ^ hour. As long 

 thereafter as the glassware remains wrapped it may be considered sterile. 



2. Hands : A surgeon often spends as much time scrubbing his hands as in operating, 

 and such cleanliness In experimental embryology will lead to more dependable 

 results. The formaldehyde, osmic or hydrochloric acid fumes, adherent to the 

 hands, will contaminate the instruments and ultimately the embryos. 



3 . Instrumente : If the Instruments have never before been used, they may be 

 thoroughly washed, rinsed, and sterilized in an autoclave at 15 pounds for 50 

 minutes. Following this treatment, immersion in 95^ alcohol should be suffici- 

 ent, providing they are never brought into association with any toxic materials. 

 Dissection Instruments from other laboratories cannot ever be used, for the 

 embalming fluids are very tenacious. The student should provide himself with a 

 new set of steel Instruments (not chromium plated) and keep them in a celluloid 

 or plastic tube, or in a cotton filled box, to be reserved for operations on 

 living embryos only. 



It is often necessary to preserve eggs or embiyos. The student sho\ild 

 have a "contaminated" set of instruments for handling such material, and avoid 

 handling such Instruments (or fixatives) at the same place where the "biologi- 

 cally clean" instruments are kept. 



k . Embryos : Dead or dying embryos are probably the most common source of con- 

 tamination of cultures. Ailing embryos should be Isolated, and crowding should 

 be avoided at all times. Healthy embryos may be passed through changes of 

 sterile medium to free them of possible adherent bacteria, or some stages may 

 tolerate brief immersion in hypertonic salt which seems to be an effective bac- 

 teriocidal agent. Generally such treatment Is unnecessary if other precautions 

 are taken. There is less likelihood of infection at the lower tolerable tem- 

 peratures, and when the culture dishes are kept covered. 



The sooner the student learns the significance of the term "biologically clean" the 

 sooner will he enjoy the experience of success In the various procedures outlined in this 

 book. 



