AS TO THE HEREDITY OF ACQUIRED CONDITIONS. 497 



cases to attain the age of twenty, while still preserving infantile 

 characteristics. If these deductions be true, it certainly would 

 seem as if the soma was capable of exercising a greater influence 

 upon the germ-plasm and its development than some writers are 

 prepared to admit. 



(3) There are the diseases commonly called hereditary, such as 

 gout, rheumatism, phthisis, and haemophilia. These require a little 

 consideration. The first two are due to some fault in the chemical 

 processes in the body, and at first sight seem to have little to do 

 with the subject of congenital malformations. I believe, however, 

 that this is more apparent than real, and that, as a matter of fact, 

 they are more closely allied than on tlie surface appears to be the 

 case. It is true that it is the chemical process which is at fault, 

 but the primary flaw must surely be in the laboratory in which 

 they take place. To say that we do not know the physical ex- 

 planation of the failure, is no more than to say that we have not 

 yet penetrated all the mysteries of human pathology. In the 

 hereditary cases it would seem that the parent transmits to the 

 ofi'spring a flaw or weakness in the chemical apparatus, which 

 under strain leads to its subsequent breakdown and the appear- 

 ance of the characteristic disease. Such a flaw or weakness may 

 surely with correctness be called an hereditary malformation. 

 Again, as regards phthisis, the tubercular bacillus is only one 

 factor in the disease : there must also be a suitable nidus or soil 

 for it- to take root in ; the condition of tissue, whether intestinal, 

 pulmonary, or otherwise, which provides this suitable soil is 

 often hereditary, and may fairly be looked upon as an hereditary 

 malformation. As regards haemophilia, there can be little diffi- 

 culty in seeing that the hereditary malformation consists in 

 some faulty construction in tlie walls of the blood-vessels, which 

 prevents them from behaving in the normal manner when cut 

 or torn. As regards cancer and its heredity, since we are quite 

 ignorant as to the cause of that complaint, it is useless trying 

 to form any theory to account for its transmission. In the next 

 and concluding section, I shall have to discuss the bearing of 

 these facts upon the question involved in this paper. 



LINN. JOUBN.— ZOOLOiir, VOL. XXIII . 35 



