1882.] Experimentation in Biology . 541 
see “ Night Side of Nature ”) are on record of bedridden 
invalids, lingering life away, who have jumped up and been 
permanently cured at the cry of “ fire.” Necessity is the 
mother of invention in human affairs; what is it “the 
mother ” of in animals ? Animals would jump and endea- 
vour to balance upon a shaking bough, if food were stored 
there, rather than hunger ; birds would dive into a foot of 
water if clear enough to see grain at the bottom, food not 
being obtainable in other parts of the room ; leaping from 
the ground to a bough is the first step towards leaping from 
one bough to another, and diving into one foot of water is a 
preparatory lesson to two, three, ten feet : by employing 
suitable apparatus for fixing to the animal, compulsory loco- 
motion in water — the hind limbs being rendered incapable of 
adtion, with a view to reduction in the course of generations 
— might effedf considerable modifications ; the enforcement 
of the ereCt posture by quadrupeds, at the same time, en- 
tailing total disuse of the fore limbs, not by severing the 
nerve, might be impracticable ; nevertheless appliances 
could be devised to render the lower primates habitually 
eredt. 
One experiment suggests another, and each other one 
several more, and the patience, time, and expense involved 
is surpassed only by the value of the possible result. Of 
course negative results would not repay the research, as 
maintained in the case of toxicological experiments. 
A knowledge of the plasticity of living structures is of 
fundamental importance under the present aspedt of Biology ; 
though negledting reference to natural phenomena or expe- 
rimental verification, popular conception may ill appreciate 
its extent ; realisation, however, is facilitated by an appeal 
to Surgery, — what seems more resistant than bone ? Yet 
varicose veins leave their impress on the tibia ; aortic 
aneurisms piece bone ; articulations are formed anew ; lux- 
ations obliterate the hollows made by tendons now removed 
from their normal situation ; and so forth. 
Ten years ago Dr. Ainslie Hollis wrote a series of papers 
on “Tissue Metabolism,” to the “Journal of Anatomy and 
Physiology,” the main discovery being that there prevails 
“ a general correspondence throughout the animal kingdom 
in the sequence of phenomena observable after application 
of an irritant to living surfaces.” Dr. Hollis’s investiga- 
tions in Vertebrate “ Tissue Metabolism ” related to such 
harmless parts as the “ recently-abscised tail of a decapi- 
tated newt.” His experiments on the higher Invertebrata 
were not satisfactory ; the chitinous integument interfered 
