384 TRANSMISSION 



obvious secretory function. The spleen appears to have an internal secre- 

 tion which is of influence in setting free the pancreatic ferment. Finally, 

 extracts of various nervous tissues brain, spinal cord, and sciatic nerve 

 have been found, when intravenously injected, to produce a distinct fall of 

 blood pressure, 1 whilst those of the pituitary body produce a marked rise. 



Here is a basis for possible transmission of such diseases as 

 might be connected with normal secretions, as it certainly is for 

 any external influence that could permanently affect either their 

 character or their quantity. This opens a wide field for the pos- 

 sible and permanent influence of causes of variation lying origi- 

 nally outside the germ, but whose effects are of such a nature 

 as to make themselves felt throughout the entire organism, and 

 to influence not only its development and activity but its power 

 of transmission as well. 



Akin to this is the possible effect of such chemicals as alco- 

 hol, which has specific relations to protoplasm and is one of 

 those influences that apparently are capable of penetrating to 

 the uttermost limits of the organism. Without doubt other mate- 

 rial elements of food and drink exert fundamental influences 

 of a chemical nature, whose effects may reach the germinal mat- 

 ter and thus of necessity descend from generation to generation, 

 to the distinct modification of the race. 



How races acclimate. How do races become acclimated ? 

 There are at least five methods competent to explain the 

 process : 



1. The acclimatization of all the individuals of a race, each 

 one in the successive generations separately ; 



2. Selection, obliterating such individuals as are unable to 

 acclimate successfully, thus restricting descent to the fittest ; 



3. The direct transmission of individual modifications (ac- 

 quired characters), at least in some slight degree, the accumula- 

 tion of which, ultimately produces complete acclimatization in 

 the race ; 



4. It is possible that the same causes which induce modifica- 

 tions in the individuals may also exert influences so deep-seated 

 as to affect the germ plasm directly and in this way produce all 

 the appearances of inheritance of modification ; 



1 Due probably to specific action on the heart. 



