CIRCULATION OF THE BLOOD. 363 



Having now given some preliminary directions that may be 

 required by the microscopist for the dissection of important 

 parts of animals generally, it only remains to describe the 

 best method of proceeding to procure certain weU-known 

 preparations from particular individuals ; these wUl be referred 

 to separately in that part of the work devoted to the prepara- 

 tion of objects of great interest. 



CHAPTER XV. 



METHODS OF EXHIBITING OBJECTS OF INTEREST. 



The Circulation of the Blood. — This wonderful phenomenon, 

 although insisted on by the immortal Harvey, was never 

 witnessed by him : it appears to have been first discovered in 

 the water newt, by Mr. William Molyneux, in the year 

 1683.* Leeuwenhoek, the father of microscopical discoveries, 

 was cognizant of it, and in his works are given both illustra- 

 tions and descriptions of the method of examining it in a 

 little fish and in an eel ; it was also the most favourite object 

 for exhibition with the older microscopists, and every instru- 

 ment was provided with itB fish pan and its tube for small eels. 

 In more modem times the frog has been principally used for 

 the purpose; and by the achromatic compound microscope 

 the circulation has been witnessed in some of the smaller 

 mammalia, in insects, in Crustacea, and even in animals as low 

 in the scale as the polypiferous zoophytes. 



In certain spiders and insects the circulation may be shown 

 by placing them, without water, in an animalcule cage (which 

 wiU be found to answer the purpose of the live box of the 

 older microscopists), or they may be held by the forceps ; in 

 some spiders it may be seen in the legs; in insects in the 

 transparent wings and antennae, and sometimes in the legs : 

 * Philosophical Transactions, vol. xv., p. 1236- 



