Osseous System.. 167 



Tin- first ribs of the chameleons ure joined in front to the sternum, 

 but the rest are joined each to its antagonist, so that each pair forms a 

 hoop. 



In the crocodiles there are the ordinary true ribs which articulate in 

 the ventral (front) side of the animal with the sternum, and the false 

 ribs which are connected (on each side) with each other at their extrem- 

 ity by cartilage, and besides these are others which protect the abdomen 

 by being buried in the muscles across the ventral parts but do not 

 extend to the spine at either end. "They appear to be produced by 

 the ossification of the tendinous extremities of the straight muscles." 

 (Cuvier, Animal Kingdom, p. 261.) It would appear that animals, 

 whose abdomen rests more or less completely on the ground, by such 

 habits differentiate muscle fibre into rigid bony tissue capable of resist- 

 ing pressure. And that they should take the shape of transverse ribs 

 instead of plates, is obviously a consequence of the lateral oscillation of 

 the body from side to side in turning and bending, by which the mate- 

 rials of the tissues are compressed into transverse creases of varying 

 density and again stretched with varying elasticity ; a process which 

 consigns certain tissues to an abnormal molecular activit} r , by which the 

 usual nutrition of muscle tissue is prevented or suspended, and a dis- 

 eased or unusual deposit of organic or mineral matter introduced. It 

 may seem strange to class a new and useful differentiation as a disease ; 

 but any change by which a hereditary race stritcture is in any degree 

 subverted must be classed as abnormal and therefore a disease. But 

 the question of its usefulness, which cannot be predetermined, is settled 

 subsequently by that process of actim? experiment called natural selec- 

 tion. If the disease proves a useful innovation by which the animal 

 reacts more readily than before against the stimuli of his environment, 

 he lives and transmits his peculiarity which thereafter becomes the nor- 

 mal property of the race. Otherwise it may be fatal to its possessor 

 and die with him, or if not a vital matter and yet not useful it will be 

 discouraged by a habit contrary to that which developed it, and so dis- 

 appear after a generation or two. This view finds support in the medi- 

 cal theory of tumors and other abnormal formations. Tumors are held 

 to be caused by the growth of dormant embryo cells in spots where the 

 normal activity and nutrition of the tissues is suspended. And such 

 growth may become hereditary, and children born generation after 

 generation with tumors in the same locality. 1 Cartilage from a foetus 

 may be artificially transplanted into the tissues of a mature animal and 

 there grow into a cartilaginous tumor. Cancer is the growth of an epi- 

 thelial tissue in places where from some habit of the body the usual 

 tissue nutriment is not supplied, perhaps not required. 

 1 Pepper's System of Medicine, 10G. 



