28 THE CELL DOCTRINE. 



Purkinje,* Valentin,f and TurpinJ had actually 

 called attention to the relations of the animal and 

 vegetable cell to each other. 



The preexistence of the nucleus, and the gradual 

 development of the cell about it, Valentin* had at- 

 tempted to demonstrate in the case of pigment cells, 

 C. 11. Schultz in the blood corpuscle, Rudolph 

 Wagner in the egg, and Henle in epithelium, all 

 before the work of Schleiden had appeared. Valen- 

 tin, too, had said, when describing the nucleus of 

 epidermic cells, that they reminded him of the nu- 

 cleus of the cells of vegetable tissues. Not only 

 this, but Armand de Quatrefages|| and Dnmortierf 

 had actually observed the origin of young cells from 

 the full grown, in the embryo of the freshwater snail, 

 while Valentin had furnished examples of the devel- 

 opment of fibres out of cells in muscular fibre, and 

 in the substance of the crystalline lens. In fact, as 

 stated by Dr. Waldo J. Burnett, in his admirable 

 paper,** Valentin " perceived the true physiological 



* Purkinje, in Kaschkow, Meletemata Circa Mammalium Den- 

 tium Evolutionem. Diss. Inaug., Wratis. : 1835, p. 12. 



f Valentin, Ueber den Verlauf und die Enden der Nerven, aus 

 den Nov. Act. Nat. Curios., vol. xvii: besonders Abgedruckt. 

 Bonn: 1836. 



J Turpin, Ann. d. Sci. Nat., 2. ser. vii, 207. 



g Valentin, Nov. Act., N". C., xvii, pt. I, p. 96. 



|| Quatrefages, Annales des Sci. Nat., 2 ser. ii, p. 114. 



T[ Dumortier, Annales des Sci. Nat., 2 ser. vii, p. 129. 



** Burnett, W. J. The Cell ; its Physiology, Pathology, and 

 Philosophy, as deduced from original investigations. To which 

 is added its history and criticism. A prize essay, read before the 

 American Medical Association, and published in vol. vi of its 

 Transactions. Philadelphia: 1853. 



