U58 



EXPERIMENTAL CHICK EMBRYOLOGY 



For such in vitro studies it is suggested that the whole or parts 

 of the eye of embryos ranging from 1 to 7 days be used (Dorris, 1958). 

 The eyes may be carefully dissected out in sterile chick Singer's using 

 fine glass needles. When whole eyes are transplanted, remove as much 

 of the adherent mesenchyme as possible, leaving only the ectoderm im- 

 mediately covering the optic cup. When parts of the optic cup are ex- 

 planted, it is first necessary to puncture the border of the cup with a 

 glass needle, impale the lens on the needle, and pull it out. With the 

 cup In position, the needle can be inserted between the two layers at 

 the choriold f Issues, thus isolating the retina which can be removed as 

 a firm cup- shaped structure. In the older eyes the lens can be removed 

 by dissecting away the overlying ectoderm, trimming the edge of the cup 

 with fine scissors, and then separating the two layers with fine glass 

 needles. The cup, or parts of either layer, can then be cut into 

 smaller pieces for explantatlon. 



This type of study provides Information relative to the self- 

 differentiating capacities of whole eyes, and (in explantatlon of pieces) 

 to the capacity for independent differentiation of the parts of the eye. 



DISCUSSION : 



The technique of tissue culture was first used by Dr. Eoss Harrison in I907. Most of 

 the work that has been done since with this technique has been with Isolated cells of the 

 relatively older {k to 8 days) chick embryos. Only recently has Spratt (19'*-7, 19'*6) re- 

 vitalized interest in this technique by finding that the entire blastoderm of the early 

 (18 to 2k hour incubated embryo) stages could be cultured in vitro, either in toto or in 

 transected parts. 



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Camera lucida drawings of the anterior 

 portion of a living 4-somite blastoderm 

 explanted to a non-nutrient saline-agar 

 medium: a, at the time of explantatlon; 

 b, after 20+ hours' cultivation. Note 

 the failure of development and the loss 

 of organization which had been attained 

 at the time the embryo was removed from 

 its normal food supply - the yolk and 

 albiimen. Note also that presence of 

 part of the opaque area has not pre- 

 vented the characteristic "degenerative" 

 changes. 



Camera lucida drawings of a living explant 

 to a yolk-albumen extract sallne-agar 

 medium. a, at the time of explantatlon. 

 b, after 55 hours' Incubation. Note the 

 remarkably normal morphogenesis, differen- 

 tiation, and increase in size of the ex- 

 plant. The heart was beating rhythmical- 

 ly when the drawing was made. 



From Spratt 191*^7: 

 Jour, Exp. Zool. 106:514-5 



From Spratt 191+8: 

 Jour. Exp. Zool. 107:59 



Spratt (19'+7) sets up a group of criteria for the adequacy of the cultvire medium used 

 in support of development, as follows: 



