1893.] Recent Literature. 249 
series on each other. I have expressed the opinion that the shear of 
the sectorial teeth of Carnivora was produced by lateral friction 
during vertical movement of the lower tooth on the upper. I have 
also asserted that the forms of facets of limb articulations are due to 
pressure. Mr. Cary sees here the attempt to explain the origin of 
totally different structures through identical mechanical processes, and 
believes that the attempt is a failure. Were the conditions of the 
problems alike, as Mr. Cary thinks them to be, he would have good 
reason for this opinion. But the conditions in the three cases are 
entirely different, and our author’s conclusion is due to neglect of 
the elementary facts of the proposition. 
The development of conules at the points indicated by Professor 
Osborn, has been supposed by him to be due to friction between exist- 
ing ridges of enamel which cross each other when in action, at the 
points in question. In the case of the development of the sectorial 
shear, the faces between which the shearing motion takes place are 
smooth, and without ridges or crests. ence the entire surface 
receives a homogeneous friction. In the third case, that of the foot 
articulations, there is no friction, but there is pressure which when 
abruptly applied in movement becomes impact. There is really no 
parity between the three cases. 
The author of this paper also thinks that the explanation of the 
elongation of bones through use of different kinds is not a permissible 
hypothesis. He cites my attempt to account for the elongation of the 
leg bones of higher mammals through impact-stimulus ; and of other 
limb bones of other mammals through stretching.. But he does not 
prove that similar results may not flow from mechanical stresses 
applied in different ways. I suppose that any mechanical stress which 
determines nutritive processes to a part, will increase its size,- 
caeteris paribus ; and the stretch as well as the impact has this effect. 
se is a term which is too indefinite for purposes of exact demon- 
stration, and I have endeavored to reduce it to precision so far as 
regards the skeleton, by defining it as “friction, pressure and strain.” 
Precisely how these processes affect nutrition is not yet clear. We refer 
the production of various animal fluids to “secretion ”, knowing that 
the products of secretion are most various, as bile, gastric juice, saliva, 
etc. The exact cause of the diversity remains unknown. So with the 
effect of stimuli on bone nutrition, we see the cause and the effect, but 
the ultimate process, as in all nutrition, has as yet eluded our view. 
In concluding, Mr. Cary admits one of the two contentions of the 
Neolamarckians in his two closing propositions. He says “ Plasticity 
