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 



