Sheep-Killing Habit Among Dogs 



381 



in the fact that breaks in generations 

 actually do occur. That 'no family his- 

 tory' of a direct ancestor is obtained in 

 response to the usual superficial in- 

 quiries made by the practitioner of hos- 

 pital cases is not surprising; the fact 

 that a disease like his own occurs in 

 other members of the family is apt to 

 be denied (if indeed recalled) by the 

 patient under the stressful conditions 

 of the examination; the. patient often 

 exhibits the reactions of the malingerer. 

 In a few histories like that of Fig. 29, 

 II, 2 [see full report; this, by the 

 way, is a case of elephantiosis], it seems 

 probable that a generation is actually 

 skipped. This is by no means fatal to 

 the view that the disease depends upon 

 a dominant trait, for a precisely simi- 

 lar result is obtained in experimental 

 breeding of clear dominant traits, e. g., 

 in polydactylism of fowl. Occasionally 

 a dominant trait simply fails of expres- 

 sion in an individual who carries it." 



The evidence that multiple neuro- 

 fibromatosis is due to heredity is very 

 convincing and it appears to be clear 

 that it is associated with a segregation 

 in the gametes, but the authors have 

 failed to furnish proof for, their 

 theory that it behaves as a Mendelian 

 dominant. 



That same form of heredity is a cause 

 of the disease is made evident chiefly 

 by the fact that it is so very rare and 

 at the same time cases occur so fre- 

 quently grouped in the same families. 



Chronic renal troubles and cancer 



may be just as much determined by 

 faulty germ-plasm, as brachydactylism 

 or night blindness, but the two latter 

 conditions are so unusual that their ap- 

 pearance in several members of the 

 same family is at once noticed, and 

 properly ascribed to heredity. Multiple 

 neurofibromatosis is also an extremely 

 rare disease. The authors find 243 per- 

 sons described in the literature of the 

 subject. One hundred and fifty-eight 

 cases show one parent similarly affected. 

 In thirty- four cases neither parent is 

 recorded as affected. This leaves fifty- 

 one cases which were left out by the 

 authors in their "families charted." 

 Just how these surplus cases are dealt 

 with is not made clear, but it is not 

 very important as far as making certain 

 the fact that the disease is due in most 

 instances, if not in all, to some quality 

 conveyed by the chromosomes. Even 

 if there be only 158 cases out of 243 

 who are the direct descendants of 

 others similarly affected, it is over 65%, 

 and this, it must be remembered, is 

 very high, considering the rarity of the 

 ailment. Probably in the cases of neu- 

 rofibromatosis many of the remaining 

 35% can be accounted for by lack of 

 complete family data, that would show 

 reversion to germ-plasm carried in the 

 stock. Others may be new mutations. 

 Further evidence must be produced that 

 this curious disease does not often skip 

 a generation, if it is to be included 

 among the comparatively few cases of 

 undoubted Mendelian dominance in 

 man. 



Sheep-Killing Habit Among Dogs Incurable and Infectious^ 



"The continued high prices of mut- 

 ton and lamb have made it desir- 

 able that more sheep be kept on 

 the farms of the United States. 

 The excessive area of rough pasture 

 land, weedy lots, and grown-up fence 

 rows affords an excellent opportunity 

 for feeding sheep, which should be used 



in cleaning up and maintaining the pro- 

 ductivity of all such lands. Compared 

 with the United Kingdom, where there 

 is one sheep or lamb for each 2.5 acres 

 of the total land area, in the Z7 farm 

 states of the United Sates, not included 

 in the western division, there is only 

 one sheep or lamp for each 31.8 acres 



1 Condensed from Farmers Bulletin 652, Bureau of Animal Industry, U. S. Department 

 of Agriculture. 



