354 PROGRESS OF SCIENCE IN THE CENTURY. 



fully to the pioneers who began the minute analysis 

 so characteristic of the nineteenth century. Keen 

 sighted observers like Leeuwenhoek, Malpighi, 

 Hooke, and Grew, in the second half of the seven- 

 teenth century were the forerunners of modern his- 

 tology. When Leeuwenhoek demonstrated unicel- 

 lular organisms to the then young Eoyal Society of 

 London, whose members (present at the meeting) 

 signed an affidavit that they had really seen the 

 minute creatures in question, a vista was opened 

 which is still widening before us after the lapse of 

 more than two centuries. 



Steps towards the Cell-Doctrine. The word 

 "cell" (an unfortunate one at the best) was first 

 used in histological description by Hooke (1665) 

 and Grew (1671-75), but not in a very accurate or 

 definite way. Malpighi (1675) also described mi- 

 nute " utricles," some of which we should now call 

 cells. 



Leeuwenhoek (Phil. Trans. 1674) seems, as we 

 have noted above, to have been the first to describe 

 single-celled organisms. But the hint was not 

 quickly followed, for it was not till 1755 that Rosel 

 von Rosenhof described the Amoeba or " Proteus 

 animalcule." 



In his Theoria Generationis (1759) Caspar 

 Friedrich Wolff recognised the " spheres " and 

 " vesicles " composing the embryos of plants and 

 animals. But he did not discern their nature or 

 their importance. 



In 1784, Fontana discovered the kernel or nucleus 

 of the cell which we now know to be essential to 

 the vitality of any ordinary protoplasmic unit. 

 But he did not know the importance of his discovery, 



