324 MR. W. WOCDLAND ON THE [Apr. 21, 
to the rest of the body. If an organ be imbedded or otherwise 
firmly aftixed to the main bulk, it will on account of its large area 
of attachment and close apposition readily share both the eleva- 
tions and depressions incurred in locomotion—the strains and 
stresses are distributed in space and time, and hence their inten- 
sity is lessened; if, on the other hand, a massive organ be merely 
suspended from the main mass of the body, such a condition 
subjects the attachment to the influence of severe strains periodi- 
cally recurring, the direction of which approaches that of the 
resultant acceleration of the trunk during its impulsive elevation. 
The great severity of these strains on the attachment of an organ 
thus disposed will be more fully realised if it be remembered 
that, on the sudden elevation of the body, the organ possesses the 
downward velocity due to the previous depression—a momentum 
which in being destroyed throws additional strain on the means 
of support. As will be seen, the preceding remarks apply in an 
eminent degree to the testes. 
The Genitalia of Mammalia. 
The reproductive organs of the Mammalia are relatively small 
bodies of great density and, in the case of the males, compactness, 
and they primitively occupy a position similar to that found in 
the lower Vertebrata. It is, however, characteristic of the majority 
of the Mammalia that in the course of development the testes 
forsake their primitive lodgment, and migrate posteriorly and 
ventrally to the terminal periphery, where they protrude at the 
surface of the body-wall. This protrusion constitutes the scrotum, 
in the wide sense of the term, which may vary in character from 
that of a pair of small slightly-elevated areas to that of a capacious 
oval pedunculated sac. Apparently in man alone the section of 
the ccelom contained within the scrotum becomes completely 
separated off from the main cavity; in other mammals, com- 
munication is retained by means of the inguinal canal, which, 
however, is usually narrow, so negativing return of the testes to 
the main body-cavity. This feature in the case of active 
mammals possessing large testes is very important, since if the 
unattached organs were permitted to return to the main cavity, 
the forces to which they would be exposed during locomotion 
would doubtless be exceedingly detrimental—a malinfluence which 
both the narrowing of the inguinal canal and the possible tractive 
function of the gubernaculum during development safeguard 
against. In fact, contrary to the usual supposition, the internal 
and not the external situation of the testes is the source of 
danger. It will also be observed that in small animals which do 
not possess narrow inguinal canals, there is no such dire necessity 
for the restriction of the testes to the scrotal cavity, both on 
account of the smaller size of the organs and the usually less 
intense forces to which the testes are subjected. Thus, para- 
doxical as it may seem, the increased protrusion of the testes 
