1. Although the chemical action of testicular hyaluronidase peculiar to the mammal has been fairly well defined by the elaboration of numerous biochemists, its physiological significance cannot be seen as fully established.
2. The generalized concept postulated with the idea of "spreading factor", that its dispersal activity on the follicular cell-mass enclosing the ovum is a necesssary antecedent to ensure the fertilization, seems to be unjustifiable because of lack of such a cell-mass at ovulation in a number of mammalian species.
3. The object of this paper is to present the evidence of intracelullar activity of the testicular hyaluronidase indispensable for normal spermatogenesis.
4. A highly purified bovine testicular hyaluronidase was repeatedly injected to the male mouse and rabbit.
5. A remarkable disorganization was observed for a while in spermatogenic epithelia.
6. Lack of meiotic divisions or meiotic irregularities in the spermatocytes and pycnosis or nuclear fragmentation resulting further in debris formation, karyorrhexis and karyolysis of the spermatids were prevailing phenomena.
7. As a consequence, a striking decrease in number of intratubular spermatozoa and a partial infertility occurred.
8. In the sera of rabbits subjected to the injections of hyaluronidase, an antibody which inhibits the dispersal action of homologous enzyme on the follicular cell-mass of rabbit ovum was definitely demonstrated.
9. It follows, therefore, that the disintegration of spermatogenic epithelia particularly meiotic irregularities are results of inhibitory action of antibody which is formed agaist the testicular hyaluronidase administered.
10. The mechanism involved in such a relationship between spermatogenic abnormalities and antigenic effects of hyaluronidase was discussed.