6 ON THE DIFFEREXTAIL REACTION TO VITAL DYES EXHIBITED BY 



interest the inception and prosecution of much of this work, renders it an appro- 

 priate, even if inadequate, tribute to his memory. 



The reactions of the connective-tissue cells can be understood best by adopting 

 as a standard their usual behavior in an animal which has received three or four 

 moderate peritoneal doses (1 to 3 c. c. of a 0.5 per cent aqueous solution) of trj r pan 

 blue at intervals of three or four daj r s and then is anesthetized in order to study 

 pieces of subcutaneous areolar tissue. There are places where small, very trans- 

 parent sheets of this tissue, of remarkable beauty and uniform thickness, can always 

 be obtained, e. g., the investiture of the muscles of the thigh or of the spine. They 

 should be stretched very rapidly by "raying" out their edges, which, from instant 

 desiccation, adhere at once to a clean glass slide. A single drop of Locke's or other 

 isotonic solution has been previously placed on a cover, which is now inverted on the 

 stretched mount with all possible speed, is rimmed with lanoline or paraffine, and 

 the preparation pushed under the microscope lens, advantageously, but not neces- 

 sarily, upon a warm stage. The entire procedure can be executed by two persons 

 in a half minute and thus all danger of desiccation or other change of the cells 

 obviated. 



Exploration of the whole fragment by means of the low-power (80 to 100 

 diameters) should precede study with the oil, but the latter must be inaugurated as 

 soon as an impression of the low-power appearance can be registered and no in- 

 considerable numbers of both cell types rapidly passed under the immersion lens 

 in review. In no other way can a judgment of the average cell-picture be obtained, 

 and, consequently, in no other way can high-power camera drawings or paintings 

 (which must be done from the living tissue) be prepared with the conviction that 

 we have chosen a representative condition. In addition to the method of exami- 

 nation in an indifferent medium (isotonic salt) which we have just described, it is 

 also of great importance that skin samples from the identical area be counter- 

 stained " supravitally " with a freshly made normal saline solution of janus green B 

 (1 : 10,000) and a similar solution of neutral red. Janus-green preparations should 

 in some cases stand exposed to the air for two minutes in order that the reducing 

 powers of the protoplasm be counteracted by continual access to oxygen ; they are 

 then covered, drained off, and rimmed for speedy exploration with the oil. 



In preparations which are made in any of the above ways, two sharply sepa- 

 rated types of connective-tissue cells in all places make their appearance. The 

 entire ensemble of morphological characteristics which distinguish these two types 

 enables us to identify them with certainty as histiogenous phagocytes (clasma- 

 tocytcs) and as fibroblastic cells. But our criteria for cell distinction, best ex- 

 pressed perhaps by Maximow in his article of 190G, are supported and accentuated 

 by the vital slain as in no other possible way. The former cells, which unfortunately 

 can be said to have received a new designation from almost every student of their 

 anatomy and physiology, we propose to designate simply as macrophages — under- 

 standing, it is true, that under this term a rather heterogeneous group of elements 

 is included; for besides the connective-tissue macrophages at least two other impor- 



