o 



70 



PROVISIONAL HYPOTHESIS 



Chap. XXVII. 



frequent presence of hairs and of perfectly developed teeth, even 

 teeth of the second dentition, in ovarian tumours, 24 



are 



facts 

 leading to the same conclusion. 



Whether each of the innumerable autonomous elements of 

 the body is a cell or the modified product of a cell, is a more 

 doubtful question, even if so wide a definition be given to the 

 term, as to include cell-like bodies without walls and without 



nuclei. 25 Professor Lionel Beale uses the 



m 



a 



germ 



inal 



" matter " for the contents of cells, taken in this wide accepts, 

 tion, and he draws a broad distinction between germinal matte: 

 and " formed material " or the various products of 



But 



is 



doctrine of omnia cellula e celluld is admitted for plants, and 

 widely prevalent belief with re 



Virchow 



ipect 



Thus 



great supporter of the cellular theory, whilst 



allowing that difficulties exist, maintains that 



y atom of 



tissue is derived from cells, and these from pre-existing cells 

 and these primarily from the egg, which he regards as a great 



Ce !l' , Tt ! at Cells ' sti11 retainin g tne same nature, increase by 



proliferation, is admitted by almost every one. 



self-division 



But when an organism undergoes a great change of 

 during development, the cells, which at each stage are supposed 

 to be directly derived from previously existing cells, must likewise 

 be greatly changed in nature ; this change is apparently attri- 

 buted by the supporters of the cellular doctrine to some inherent 

 power which the cells possess, and not to any external agency. 



Another school maintains that cells and* tissues of all kinds 

 may be formed, independently of pre-existing cells, from plastic 

 lymph or blastema ; and this it is thought is well exhibited in 



the repair of wounds. As I have 



histology, it would be presumptuous in me 



especially attended to 



the two opposed doctrines 



express 



But every one appears 



opi 



admit that the body consists of a multitude of " organic 



24 Isidore Geoffroy St. Hilaire, « Hist. 

 des Anomalies,' torn. ii. pp. 549, 560, 

 562 ; Virchow, idem, p. 484. 



25 For the most recent classification 

 of cells, see Ernst Hackel's ' Generelle 

 Morpholog./ Band ii., 1866, s. 275. 



26 'The Structure and Growth of 

 Tissues,' 1865, p. 21, &c. 



* Dr. W. Turner, * The present 



Aspect of Cellular Pathology/ « Edin- 

 burgh Medical Journal,' April, 1863. 



28 This term is used by Dr. E. Mont- 

 gomery (< On the Formation of so-called 

 Cells in Animal Bodies,' 1867, p. 42), 

 who denies that cells are derived from 

 other cells by a process of growth, but 

 believes that they originate through 

 certain chemical changes. 



v 



l 



