1903.] TRANSPOSITION OF MAMMALIAN TESTES. 321 
its members exhibit, and by the more perfect ad: aptation of the 
body (relation of limbs to trunk, &e.) to the locomotion in which 
the superior activity is mainly manifested. Consequently, in 
mammals, the reactions which occur between the organism and 
the substratum vastly exceed in magnitude those occurring in 
lower groups, and we have in this distinction a factor which in 
considering bodily conformation is worthy of all attention. 
Since in mammals the organisation is subject to such considerable 
forces, 1b follows that if stability of position be ca in con- 
nection with organs possessing appreciable mass, ¢. e. if these 
organs are to adjust themselves to those tr: ihepaaine influences 
which arise out of impulsiveness, fixative structures must be ° 
developed in response to the demand. For, as remarked above, 
a sudden acceleration imparted to the body is necessarily trans- 
mitted to an attached organ through its attachment, which, if the 
organ be of considerable mass, is thereby subjected to an intense 
strain, possibly ending in disruption. Stability of position of an 
organ may be necessitated either on mechanical or physiological 
grounds: thus, apart from considerations of function, viscera of 
large mass (stomach, liver, intestine) must conform, as regards 
situation in the body-cavity, to the principle that, ceteris paribus, 
the more anterior the centre of gravity of the body the greater 
the facility of progression’; and again, from the functional 
standpoint, the kidneys must in active animals be maintained 
anteriorly in order to ensure proximity to a vigorous blood-supply. 
It will be evident from this, that if the position of an organ be of 
no economic moment—if there be no need of localisation ‘either on 
account of mass or volume for preservation of bodily equilibrium, 
or on account of nature of function for physiological efficiency,— 
retentive structures will not tend to be formed, and the organ, if 
of sufficient mass, will respond by transposition to any considerable 
force incident upon it—a trait which in the course of generations 
will be inherited. 
I shall now proceed to examine more in detail the production of 
the forces hitherto assumed to be capable of effecting the trans- 
position of the testes—to enquire whether the intensity and 
direction of these forces are such as are congruous with the 
hypothesis advocated, 
Mammalian Locomotion. 
In view of the importance that is here attached to the character 
of mammalian locomotion, it is needful to discuss the subject in 
detail. Every unsupported mass descends to the earth with a 
given acceleration, and the magnitude of the force required to 
re-elevate the body to its initial position is directly proportional 
1 Well shown by measurements of the position of the centre of gravity in Pisces, 
and by the abdominal contours of active cursorial mammals as compared with those 
of species more slothful in habit (compare e.g. a greyhound or race-horse with a 
St. Bernard or cart-horse, or , more generally, herbivores with carnivores, though 
the different capacities of the dige stive organs have here to be eausidsyred), 
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