342 ANNUAL OF SCIENTIFIC DISCOVERY. 



many persons use but one eye for taking their direction in vision, and 

 that is generally the right ; it is sometimes the left, but in normal 

 instances an object is seen in the median plane between the two eyes. 

 Many persons have the idea that stereoscopic vision is only squinting, 

 but this is very far from being the case ; in squinting, the eyes con- 

 verge to a point nearer than that of distinct vision ; in stereoscopic 

 vision the eyes are not so directed, and the sense of fatigue and dis- 

 comfort is owing to the forcible dissociation of two naturally associ- 

 ated actions. In common vision there are two adjustments, one con- 

 sisting in directing the optic axes to the object, the other in adjusting 

 them to suit the distance of the object from the eyes, drawing them, 

 so to speak, out or in like the joints of a telescope ; habit enables us 

 to eifect these two adjustments instantaneously and at the same time. 

 In looking through a stereoscope, while the object is very near, we 

 are forced to extend our optic tubes to see an object apparently at a 

 great distance, and thus the union of the associated motions is vio- 

 lently broken up, causing a sense of fatigue. 



PHYSIOLOGY OF WIDOWHOOD. 



A correspondent of the London Medical Times and Gazette thus 

 writes in relation to the above subject : 



For some time past my attention has been attracted to a very 

 curious form of hereditary transmission of physical peculiarities, 

 which I think worth while to lay before the profession, that more ex- 

 tensive and more accurate investigation than I can accord it may, if 

 not exactly, at least proximately, determine its value as an influence 

 in the production of disease. 



Lord Morton bred a hybrid from a chestnut mare and male quagga 

 the hybrid was quagga-like, and even the foals subsequently pro- 

 duced from the mare by a black Arabian sire were " much more plain 

 barred across the legs than is even the pure quagga," Now, here is 

 an instance of the positive transmission by the female of one species 

 of the physical peculiarities of the male of another species, with whom 

 she had bred, to her offspring by a subsequent union with a pure male 

 of her own species. This in itself is not a little remarkable, and 

 worthy of investigation, by those who have opportunity, amongst mule- 

 breeders and others; but, further, I have made many inquiries 

 amongst those interested in the pure breeds of all kinds of cattle, 

 sheep, dogs, poultry, pigeons, etc., and they universally declare that 

 if a high-bred female once breeds with an inferior male, even of her 

 own race, she will never produce pure offspring, though she always, 

 subsequently, breed with males of the highest caste. Thus, if a thor- 

 ough-bred mare have a colt whose sire is a half-bred horse, though 

 she subsequently breed with only thorough-bred horses, her foals will 

 never prove thorough-bred. An instance was lately mentioned to me 

 much in point, where a very pure-bred setter bitch produced her first 

 litter after a cur dog, and, though subsequently put to some of the best 

 setter dogs in the kingdom, her puppies were never pure or worth 

 keeping. We know that the greyhound breeders cross with a bull- 

 dog to give their greyhounds courage and tenacity of purpose, and 

 that it does this for many generations ; but that it is effected by 



