386 MACROPHAGES FROM ARACHNOID CELLS. 



macrophages is not so great as in the above experiments, but one comes upon the 

 same swelling up of the protoplasm and phagocytosis of granules by the cells found 

 on the trabeculse. The arrangement of the ingested particles tends to be close to 

 the nucleus and consists of the smaller granules. Weed (1917, p. 470) noted, a few 

 hours after injection, "particles of carbon in the cuboidal cells of the arachnoid 

 and similar pictures after the injection of cinnabar." Inert participate matter 

 which could be easily identified in the tissue has been employed by many observers 

 in the study of the drainage of cerebro-spinal fluid, by injection into the sub- 

 arachnoid space. Quincke (1892, p. 159) remarks: 



"Ausserdem fand sich Zinnober in rundlichen oder unregelmiissig gestalteten Zellen, 

 die, etwas grosser als Lymphkorperchen regellos verstreut im Subarachnoidalgewebe 

 vorkommen, bald einzelen bald gruppenweise: und die wohl als Bindegewebszellen von 

 veranderlicher Form anszusehen sind." 



Unable to convince himself that the sessile cells took up any of the granules, 

 he concludes (p. 176) : 



"In den eigentlichen Epithelien der Dura oder Arachnoidea konnte der Farbstoff nie 

 sicher nachgewiesen werden, wenn auch oft genug zinnoberhaltige Zellen der Epithel- 

 schicht aufsassen. Ebensowenig fand sich Zinnober in den grossen spindelformigen Zellen, 

 welche bei jiingeren Thieren die Bindegewebsbalken des Subarachnoidalgewebes bilden, 

 noch in jenen blassen, epithelartig angeordneten Zellen, welche die bindegewebigen Mashen- 

 raume dieser Membran auskleiden." 



The failure of Quincke was probably the result of waiting too long to study 

 the material i. e., in periods of a week or more. It appears that the reaction of the 

 membrane is less vigorous after a certain number of cells have become free in the 

 locality; this phenomenon is strikingly illustrated where inert particles are used. 

 Introduction of vital stains into the subarachnoid cavity has not shed any further 

 light on the physiological activity of the lining membrane. Goldmann (1913) makes 

 no mention of vital staining of the meninges. The toxicity of the stain for the 

 nervous system may account for this, as the animals die very quickly after the 

 injection. 



The experiments furnishing the material for this paper must be regarded as too 

 acute to shed much light on the fate of these cells which have separated themselves 

 from their normal environment. The use of insoluble inert matter furnished a 

 means of determining this and such a key is found in the work of Quincke. After 

 months these wandering cells may be found, with their cinnabar inclusions, along 

 the carotid sheath to cavernous sinus, along intercostal nerves several millimeters 

 beyond the junction of the sympathetic chain, plexus lumbalis, upper cervical 

 lymphatic and submaxillary lymphatic glands. This shows that the process of 

 migration is slow and dependent on the amoeboid activity of the cells themselves. 

 The ultimate disposition of such insoluble matter must be a process similar to the 

 storage of dust inhaled into the lungs. The soluble matter (in the laked corpuscles 

 used) is promptly digested and only the iron pigment remains. No evidence was 

 obtained in support of a view that the free cells after leaving the trabeculse would 

 again assume their former position. 



