132 Mr. W. Wliitaker on some Surrey Wells. 



But it was never possible to demonstrate the existence of this 

 substance. Moreover, some diseases do not protect against 

 themselves, or even are more prone to return, and yet run their 

 course and die out. Another theory was that the bacteria added 

 something to the system which not only killed them, which we 

 Imow is the case among saprophytes, but, remaining in the 

 system, prevented any future invasions. But here again no 

 analysis could find the substance. Another theory is more 

 tangible. It is known that the bodies described as leucocytes 

 and white-blood corpuscles incorporate foreign bodies, and it has 

 been shown in experiments upon animals that the living cells do 

 swallow the bacteria. This is Metschnikoff's theory of Pharjo- 

 cytosis. He considers that the corpuscles by practice acquire this 

 power of swallowing and destroying bacteria ; that they always 

 do so during the convalescence from infectious diseases ; but that 

 till they have thoroughly "learnt the trick" they cannot keep 

 down the invading bacteria. This theory supposes that the work 

 once learnt is handed down from one generation of corpuscles to 

 another. The old pathological schools are at the present day 

 represented in this question of immunity: the " solidists" holding 

 that it is the living tissues of the body which, in exercise of their 

 subtle vigour, act the part of a defending army ; the "fluidists " 

 maintaining that the serum of the blood has a bactericidal 

 action. In any case we must come fundamentally to the living 

 body-cells, which are responsible for the composition of this 

 serous medium. 



117. — Some Surrey Wells. (Second Paper.) 



By W. Whitaker, B.A., F.E.S., F.G.S., Assoc. Inst. C.E. 



(Bead November 20th, 1894.) 



Op the following sections the only one calling for particular 

 notice is at East Horsley, where the Chalk has been pierced from 

 top to bottom, from the Tertiary beds above to the Upper Green- 

 sand beneath. Only in two other places in the county had this 

 happened before, at Richmond and at Streatham. But whereas in 

 those sections the Chalk is about 670 and 623 feet thick, at East 

 Horsley it is over 817, an increase of 147. The Earlswood boring, 

 throughout in Wealden beds, is also notable on account of its 

 depth ; and the Richmond well because it is the first experiment 

 in driving a great length of galleries in the Chalk beneath a great 

 thickness of Tertiary beds, that thickness varying from 250 to 

 300 feet ; whereas in other places no such extensive work has 



