AbstractsBiology & Animal Science

Morphological changes corresponding to functional activity have been found by numerous investigators. The purpose of this investigation was in the first place to determine, if possible, at what period functional activity might begin. The second aim was to investigate to what extent early changes of function correspond to adult changes and to trace the progress of development. This has been done principally in terms of the nucleus-plasma relation theory of Richard Hertwig. This article is based principally on the study of puppies from the foetus to four weeks. In addition to dogs; cats and rabbits have been used. The kitten-at birth was used principally for comparison and its cells were not studied in detail. The rabbits served largely for the purpose of learning technique. Over one hundred cells were measured in addition to drawing the several stages. The animals used are listed below in order of advancing age.