GENIC ACTION IN THE MOUSE 231 



obtained by using some of the other methods of which Dr. Russell spoke, more specifi- 

 cally, retrograde analysis and possibly transplantation. 



Dr. Burdette: Do you find very often that the same sort of pathway is present 

 clinically in patients as in the murine condition ? 



Dr. Russell: In the mouse there is a similar triad of pleiotropic effects 880, 1097 ' 

 ii55, 1207 j n two distinct hereditary anemias. One is the W-series anemia, the other 

 the ^/-series anemia. We know the two anemias are not identical since they are 

 produced by completely nonallelic genes. However, it does seem to me quite probable 

 that these two genes may very well affect different steps in the same synthetic process. 

 It is possible that there are also human anemias of maturation arrest very similar to 

 these conditions in the mouse. These humans might also fail to respond to erythro- 

 poietin. One reason for thinking this is that there are many essential anemias in 

 which affected individuals excrete erythropoietin; and, if they are excreting large 

 amounts of this substance, it is probable that they cannot respond to it, even though 

 they are producing it. If histocompatibility could be sufficiently controlled in man, 

 there might be some purpose to therapy of human anemia by implantation of blood- 

 forming tissue. However, one would have to know a great deal more about human 

 histocompatibility than is now known before one could possibly determine if this 

 method would be useful. The answer to Dr. Burdette's question will be more apparent 

 when more information concerning human histocompatibility is forthcoming. 



Dr. Wright: The ordinary albino guinea pig has no pigment at birth but later 

 develops considerable pigment on feet, ears, nose, and even back. This is definitely a 

 temperature effect, as Dr. George Wolff and others 1401, 1437 showed; there are two 

 other alleles, c r and c d , both of which lead to increased intensity after birth. This 

 darkening of the c d and the c T genotypes is definitely a temperature effect again as Dr. 

 Wolff has demonstrated. Thus there are three alleles among the five in a guinea pig 

 that presumably have thermolabile products. They are low in pigment-producing 

 capacity up to birth. They immediately begin to produce much more afterwards 

 which can be prevented by high temperature. Most of the other changes in color are 

 independent of temperature. Sootiness in yellow guinea pigs, however, and also 

 yellow in the rabbit, as demonstrated many years ago by Walter Shultz, 1176 are 

 apparently dependent on a temperature effect. The thermolability in these cases is 

 entirely independent of that of c genotypes. 



Dr. Pilgrim: Have other heat-labile tyrosinases been found in other Himalayan 

 albinos or in other species ? 



Dr. Russell : I do not know of any extracted tyrosinase experiment in another 

 mammal. Of course there is thermostable and thermolabile tyrosinase in Neurospora 

 which is the inspiration for this investigation in the mouse. 



Dr. Ginsburg: Nachtsheim found that the blue-eyed white rabbit is highly 

 susceptible to seizures, both sound-induced and spontaneous. 929 However, in a 

 survey of the races, including various pigment types in Dr. Paul Sawin's very representa- 

 tive rabbit colony, susceptibility to these types of seizures has been found in almost all 



