( 814) 



Comparing the puerperal involution of the uterus of the hecU/ehog 

 with the same pjrocess as it occurs in other mammals, hitherto studied, 

 loe may state that in this respect the hedgehog occupies an intermediate 

 position between Rodents and Carnivora. It stands near the former 

 in the way in ivhich the epithelium, regresses, near some of the latter 

 in the regression of the layer of connective tissue, although in this 

 respect the analogy is not complete. 



The more accurate details of the involutional processes of whioii 

 a short sketch is given here, will be published elsewhere. 



Physics. — "Magnetic resolution of spectral lines and magnetic 

 force". Bj Prof. P. Zeeman. (First part). 



The intensity of a magnetic field may be defined by the amount 

 of splitting up of a given spectral line emitted by a source placed 

 in the field. 



The distance of the outer components of a triplet can be measured 

 Avith great accuracy. The components of a line resolved by the 

 action of magnetism are of the same width as (he original line and 

 the high degree of accuracy obtainable in the measurement of spec- 

 trum photographs is generally known. 



We may call two magnetic intensities equal, when producing 

 equal amounts of separation of a spectral line, and we may call 

 two differences of magnetic intensifies equal, when the changes of 

 the distances of tlie components are the same. In this way we 

 obtain a scale of magnetic forces, the zero point and the magnitude 

 of the units can still lio\\'evei' be chosen arbitrarily. All conditions 

 necessary for the imlirect comiiarisou of different intensities of a 

 quantify are fultilied. ') 



In this method of measuring magnetic forces we adopt a natural 

 unit of magnetic foi'ce. 



In applying the specified method we need not know the functional 

 relation between magnetic force and magnetic separation of the 

 spectral lines. It is sufficient to know that this function is one- 

 valued. The most accurate measurements of the present time °) 

 and also theory render it extremely probable (hat tlie separation 

 of the spectral lines is proportional to the intensity of the field 

 wherein the source of light is placed. If this simple relation be 



1) Comp. RuNGE, Maass unci Mes.sen. Encyclopiidie der mathematiscliou Wisseusch. 

 Bd. V. I. 1903. 



~) See specially : A. Farber, Uber das Zeeman-Plianomen. Ann. d. Phys. 9 

 p. 886. 1902, 



