Abstract
1. Cyclophosphamide (0.05mg in 0.04ml of normal saline) was injected into yolk sac of chick embryos on day 0-5 of incubation and brains of these embryos were collected on altemate days from day 9 to 21 of incubation. 2. On macroscopic examination, micrencephaly of variable degree was detected resulting from reduced dimensions of the brain and its different parts. 3. The degree of micrencephaly varied with the time of incubation at which cyclophosphamide was injected. It was most marked in the brains treated on day 0 and 1 of incubation. The brains treated on day 5 were next in order of retardation though treatment on day 2, 3 and 4 also significantly reduced the size of brains. 4. The length and breadth of cerebellum, length of cerebrum and total length of brain were the most affected measurements. Weights of the brains also showed corresponding reduction in the treated groups. 5. Micrencephaly in the treated groups was evident even in the earliest collected specimens, i.e., on 9th day of incubation though it became more marked as the incubation advanced. 6. In general, the maximum reduction in size was noted about the 15th day of incubation after which the degree of retardation decreased indicating beginning of recovery from the suppressive effect of the drug.
