350 



the sut. parietalis and other abnormalities of the skull of man and 

 monkeys, are missing here. The interparietal seems to be a little 

 bigger than is usually the case with white rats. 



The skull is in the museum of the Zootomical Laboratory at 

 Leiden, Holland. 



The superfluous suture, which is mentioned here, divides the 

 parietale sinistra in two parts, almost equal. If one wishes to follow 

 the division of Hrdlicka of the sut, par. in horizontal (with the sut. 

 sagitt. about parallel), perpendicular (about perpendicular on the sut. 

 sag.) and in oblique, in different directions, then this suture must be 

 taken with the latter. When judging superfluous sutures one must 

 always be very careful and eventually exclude fractures in the skull. 

 Sometimes this causes great difficulties and one does not know 

 whether it is a fracture or a superfluous suture on the parietal 

 Hedlicka (6) describes a useful example of it, and gives pictures 

 About the cause of the origin of the sutura parietalis we are still 

 uncertain. Yet Hertwig (9) says on pg. 848: "Das os parietale 

 bipartitum mit horizontaler Naht erklärt sich am einfachsten aus der 

 Annahme, daß abnormerweise die Vereinigung beider Zentren (of the 

 parietal) unterbleibt. Nach Schwalbe ist unter den dabei in Betracht 

 kommenden Bedingungen mit großer "Wahrscheinlichkeit ein patho- 

 logisches Moment, eine im embryonalen Leben auftretende Hydro- 

 cephalie verantwortlich zu machen. " With regard to man this seems 

 to be true, but with regard to monkeys, Hrdlicka (6) decidedly denies 

 "ein pathologisches Moment". It seems to me rather important to 

 tell a little about the descent of the skull of the white rat which I 

 found. The skull belonged to a specimen- of a rather numerous colony 

 of white rats, which is kept in the Zootomical Laboratory at Leiden. 

 This colony descends from one couple and for some years has always 

 multiplied by inbreeding. This does not seem to be good for them 

 in the long run, at least, I saw the following more or less patho- 

 logical phenomenons: a slanting muzzle, scarce growth of hair, and 

 bald spots on the skin, many and still increasing inflammations of the 

 eyes, blindness, specimens with "tusks", and finally the fertility is 

 decreasing; births are rarer and the number of young ones of one 

 litter also decreases. 



These things seem to refer to a certain putrefaction of the colony 

 and this putrefaction is perhaps " ein pathologisches Moment " through 

 which, with this rat, the sutura parietalis has occurred or the occur- 



