RECENT TENDENCIES IN BIOLOGY 439 
tire histological elements so that they may be viewed as solids 
has come to supplement the study of sections. Reconstruc- 
tion, by carving wax plates of known thickness into the form 
of magnified sections drawn upon their surfaces to a scale, 
and then fitting the plates together, has been very helpful in 
picturing complicated anatomical relations. This method 
has made it possible to produce permanent wax models of 
minute structures magnified to any desired degree. Minute 
dissections, although not yet sufficiently practiced, are never- 
theless better than the wax models for making accurate 
drawings of minute structures as seen in relief. 
The injection of the blood-vessels of extremely small 
embryos has made it possible to study advantageously the 
circulatory system. The softening of bones by acid after 
the tissues are already embedded in celloidin has offered a 
means of investigating the structure of the internal ear by 
sections, and is widely applicable to other tissues. 
With the advantage of the new appliances and the new 
methods, the old problems of anatomy are being worked over 
on a higher level of requirement. Still, it is doubtful whether 
even the old problems will be solved in more than a relative 
way. It is characteristic of the progress of research that as 
one proceeds the horizon broadens and new questions spring 
up in the pathway of the investigator. He does not solve 
the problems he sets out to solve, but opens a lot of new ones. 
This is one of the features of scientific research that make 
its votaries characteristically optimistic. 
Experimental Work.—Among the recent influences tend- 
ing to advance biology, none is more important than the ap- 
plication of experiments to biological studies. The exper- 
imental method is in reality applicable to diverse fields of 
biological research, and its extensive use at present indicates 
a movement in the right direction; that is, a growing interest 
in the study of processes. One of the earliest problems of 
