STRUCTURE AND GROWTH OF DOMESTICATED ANIMALS. 649 
all knowledge, that it should be acquired, not only in its general 
features, in order to be useful, but that it should be brought to a 
point where it shall be really applicable to any practical purpose ; 
and a great deal of the difficulty in scientific investigation arises 
from the fact, that while it is easy to study, to a certain extent, 
it is not always easy to carry our knowledge to the point where 
its application becomes easy or even practicable. And I would 
say, to exonerate science from its failure to make itself more gen- 
e-ally popular and practical, that the mental qualities required for 
investigation are not the same as the qualities required for prac- 
tical application. You know too much of practical life to need to 
be told that the importers who bring to your manufacturing estab- 
lishments the raw materials are not those who make the cloth for 
your clothes; or that those who import the raw materials with 
which all the various manufactures are produced are not likely to 
be themselves manufacturers ; and the ability of the one excludes 
very often the ability of the other. In scientific matters this is 
perhaps more extensively the case than in practical pursuits, so 
that a class of men must be educated who will take up knowledge 
where the scientific man leaves it, and carry it where the man of 
business, or the practical man, requires it. I could mention many 
a case in which scientific men have injured themselves in their 
attempts to derive profits from their scientific work or to apply 
their knowledge to practical purposes. That will happen again 
and again when scientific men rashly enter the arena of practical 
life. You must allow them to work in the field for which they 
were prepared, and accept from them what they can give. I claim 
that as due to science, and I think the sooner the community un- 
derstands it the sooner will all have the benefit of what science 
can produce, and cease to ask the impossible from scientific men. 
In this first presentation of the subject of embryology I shall 
not be able to give the whole history of the formation of a new 
being, but only so much of it as will. satisfy you that our higher 
animals produce eggs like birds and the lower classes; but with 
this essential difference, that in mammalia the fecundated egg is 
not cast or laid, but undergoes all its changes within the maternal 
body until the living youngis dropped. Here are several figures of 
Ovarian eggs of the dog, rabbit and human female, which may easily 
be compared with the eggs seen in the ovary of a hen. Figures 
154, 155, 156; 157, 158, 159, 160 and 161 are such ovarian eggs. 
