482 Miscellaneous. 



According to the statements to which I have just alluded, these 

 structures should he chiefly found in the frontal lohe *, where they 

 ought to appear particularly abundant ; now the histological exami- 

 nation of this region brings to light three kinds of nervous 

 elements : — 



1. Normal nerve-cells, generally unipolar or bipolar, with a bulky 

 body and a globular nucleus, the chromatic power of which varies 

 according to the development of the nuclein substance. 



2. Other nerve-cells, differing from the foregoing by the existence 

 of two or several nuclei. These nuclei are feebly stainable by the 

 colouring reagents ; the nuclein substance is here found to be fre- 

 quently represented by ovoid corpuscles, as may be demonstrated by 

 the aid of a good immersion objective. 



3. Little cells, measuring on an average 4 ji, and possessing so 

 large a nucleus that the body of the cell is frequently found to be 

 reduced to a delicate peripheral layer of protoplasm. These cells 

 reproduce fairly well the old type termed myelociite. 



We observe that these various elements are distinctly cellular and 

 that it is impossible to admit the existence of free cerebral nuclei. 

 This conception is without doubt the result of a hasty and incom- 

 plete study of the third histic form which has just been described. 

 In reality wherever nuclei appear they are accompanied by a proto- 

 plasmic mass, the boundaries of which, though often difficult to 

 follow, are nevertheless incontestalde. 



The comparative histology of the principal groups of Invertebrates 

 had, moreover, established during the last few years f the existence 

 in them of elements identical with those which, in the case of 

 Myriopods, have been pointed out as new and of a special character. 

 It is sufficient in all these cases to multiply observations, in order 

 to perceive that the pretended free nuclei become united by means 

 of numerous transitional forms to the normal t5'pe of nerve-cell ; 

 they represent nothing but a simple variety of the latter. — Comptes 

 Eendus, t. cxvii. no. 5, July 31, 1893, pp. 291-293. 



* It would be necessary to formulate certain reservations with respect 

 to the employment of this term and to the limits of the region which it 

 serves to designate ; but I have not to consider here the details apper- 

 taining to the descriptive anatomy of the nervous centres in Myriopods. 



t Joannes Chatin, " Sur les My6locytes des Invert6br6s," Comptes 

 Rendus, 1888. 



