SCHWANN 173 



Valentin l appears to have seen cells in cartilage and 

 epithelium even before Henle, and to have observed cells in 

 the blastoderm of the chick. In his report on the progress 

 of anatomy during 1838 Johannes Miiller was able to refer to 

 quite a number of papers dealing with the occurrence of cells 

 in animal tissues. In addition to those already noted, he 

 mentions work by Breschet and Gluge on the cells of the 

 umbilical cord, by Dumortier on the cells in the liver of 

 molluscs, by Remak and by Purkinje on nerve cells, by 

 Donne on the cells of the conjuctiva, cornea and lens. He 

 reports, too, that Turpin had compared the epithelial cells of 

 the vagina with the cell-tissue of olants. Miiller himself had 



O A 



not only recognised the cellular nature of the notochord, but 

 had observed the cells of the vitreous humour, fat cells and 

 pigment cells, and even the nuclei of cartilage cells. From 

 Schwann (1839) we learn that C. H. Schults had followed 

 back the corpuscles of the blood to their original state of 

 nucleated cells, and that Werneck had recognised cells in the 

 embryonic lens. A preliminary notice of Schwann's own 

 work appeared in 1838 (Froriep's Notisen, No. 91, 1838), the 

 full memoir in 1839, under the title Mikroskopische Unter- 

 sucJiungcn fiber die Uebereinstimmung in der Struktur und 

 dem WacJistume der Tiere und Pflanzen? 



Theodor Schwann was a pupil of Johannes Miiller, and 

 we know that Miiller took much interest in the new his- 

 tology. It is probably to his influence that we owe Schwann's 

 brilliant work on the cell, which appeared just after Schwann 

 left Berlin for Lowen. Schwann was himself, as his later 

 work showed, more a physiologist than a morphologist ; he 

 did quite fundamental work on enzymes, discovering and 

 isolating the pepsin of the gastric juice ; he proved that 

 yeast was not an inorganic precipitate but a mass of living 

 cells ; he carried out experiments directed to show that 

 spontaneous generation does not occur. We shall see in his 

 treatment of the cell-theory clear indications of his physio- 



1 See Schwann's Bemerkungcn at the end of his Mikroskopische 

 Untersuch ungen. 



2 Republished in Ostwald's Klassiker der exakten Wissenschaften, 

 No. 176, Leipzig, 1910. References in the text are to the original 

 pagination. 



