A478 ORREN LLOYD-JONES AND F. A. HAYS 
progress. The sperm is oriented by currents which exist in the 
genital tract, as Kraft showed in 1890 (p. 216). He flooded a 
piece of uterine mucous membrane from a freshly killed cow 
with an isotonic salt solution and when rabbit sperm were placed 
thereon, they were observed to swim rapidly against the currents 
set up by the cilia of the membrane. Roth recorded a similar 
observation in 1893 (p. 352). 
Pronounced motility may be in most cases accepted as evidence 
of the fertility of the male, but this is not always the case. For 
example, Detlefsen (14, pp. 91-93) found in case of his hybrid 
guinea-pig males that though the presence of a high percentage of 
normal active spermatozoa in the fluid obtained from the epi- 
didymis was as a rule a very good indication of breeding power, 
nevertheless 10.2 per-cent of such hybrid guinea-pig males were 
completely sterile though a copious supply of active sperm was 
present. And Reynolds (16), after extensive studies on the ques- 
tion of sterility in the human subject, insists that the mere pres- 
ence of active spermatozoa in the semen of a man is by no means 
certain evidence of his power to reproduce. He considers that 
investigations as to fertility, must take into account not only the 
existence of motility, but the duration of motion and still more 
the quality of motion present. 
In regard to quality of motion, several writers have observed 
that various categories may be made out. As long ago 4s 1856, 
Kolliker in his description of the stimulus which certain sub- 
stances produce in mammalian sperm, distinguished between an 
‘axedrehung’ and a ‘Schlange bewegung,’ and Iwanoff (07) 
emphasizes the importance of ‘mouvements progressife’ in con- 
trast to ‘mouvements vibratior.’ But Reynolds’ (’16) obser- 
vations have been much more extensive and his interpretations 
more suggestive than those of other writers and his work de- 
serves further mention. Reynolds’ studies are based upon the 
examination of 45 specimens of semen from man collected some- 
times free from the secretions of the female and sometimes mixed 
with these secretions. His studies have led him to the ‘positive 
differentiation’ of 5 types of motion, 3 of which he considers as | 
