180 DISEASES OF OATTLE. 



(8) Prom imperfect differentiation of the sexual organs — hermaphro- 

 dites (organs intermediate between male and female), male organs 

 with certain feminine characters, female organs with certain well- 

 marked male characters. 



(9) Prom the doubling of parts or of the entire body — double mon- 

 sters, double heads, double bodies, extra limbs, etc. — redundant 

 development. (PI. XIX, figs. 1, 2, 3.) 



Causes. — The causes of monstrosities are varied. Some, like extra 

 digits, lack of horns, etc. , run in families, which produce them with 

 absolute certainty when bred in the direct, line, although they were 

 originally acquired peculiarities, which have merely been fixed by 

 long habit in successive generations. The earliest horse had five toes, 

 and even the most recent fossil horse had three toes, of which the two 

 lateral ones are still represented in the modern horse by the two splint 

 bones. Yet if our horse develops an extra toe it is pronounced a 

 monstrosity. A more genuine monstrosity is the solid-hoofed pig, in 

 which two toes have been merged into one. Another of the same kind 

 is the solid shank bone of the ox, which consists of two bones united 

 into one, but which are still found apart in the early fetus. Though 

 originally acquired peculiarities, these now breed as invariably as 

 color or form. 



Other monstrosities seem to have started in too close breeding, by 

 which the powers of symmetrical development are impaired, just as 

 the procreative power weakens under continuous breeding from the 

 closest blood relations. A monstrosity consisting in the absence of 

 an organ often depends on a simple lack of development, the result 

 of disease or injury, as a young bone is permanently shortened by 

 being broken across the soft part between the shaft and the end, the 

 only part where increase in length can take place. As the result of 

 the injury the soft growing layer becomes prematurely hard and all 

 increase in length at that end of the bone ceases. This will account 

 for some cases of absence of eye, limb, or other organ. 



Sometimes a monstrosity is due to the inclosure of one ovum in 

 another while the latter is still but a soft mass of cells and can easily 

 close around the first. Here each ovum has an independent life, and 

 they develop simultaneously, only the outer one having direct con- 

 nection with the womb and being furnished with abundant nourish- 

 ment advances most rapidly and perfectly, while the inclosed and 

 starved ovum is dwarfed and imperfect often to the last degree. 



In many cases of excess of parts the extra part or member is mani- 

 festly derived from the same ovum, and even the same part of the 

 ovum, being merely the effect of a redundancy and vagary of growth. 

 Such cases include most instances of extra digits or other organs, 

 and even of double monsters, as manifested by the fact that such 

 extra organs grow from the normal identical organs. Hence the 

 extra digit is attached to the normal digit, the extra head to the one 



