1888.] MICROSCOPICAL JOURNAL. 51 



hand for filtering first tlirough paper tlie solution will be clearer, although 

 this is not absolutely essential. 



We have a gelatino-chloride of silver emulsion, with a slight excess of silver. 

 It need not be kept from the light, but is best, I think, when fresh, I have 

 some dried on glass plates which I believe will keep indefinitely. 



The particles of chloride of silver are exceedingly minute — indeed with a 

 quarter inch looks like a solution. Of course it must be used warm like all 

 gelatin masses. The color in the mounted section is of a beautiful purple and 

 perfectly ti-anslucent. The differentiation between aiterioles or venules and 

 capillaries by its means is perfect, — as the larger the vessel, the darker the 

 color of the mass. I have not yet found it necessaiy to take any special pains 

 to darken the injection by exposure to light — the excess of silver seems suf- 

 ficient to cause the reduction of the chloride. There is absolutelv no such 

 word as fail in connection with its preparation, although the order given 

 must be observed with reference to the citric acid. This nnist be put in last, 

 and this is the only important matter. Certainly metal vessels must not be 

 used as the silver salt would act upon them. Do not infer that the mass is 

 spoiled if partly darkened before use. 



I have had this in use for nearly two years, but have not made it public, as 

 I have not been able, until quite lately, to spare tlje time to thoroughly test 

 its properties. It will give me pleasure to suggest any fiu'ther details if 

 thought necessary. 



410 E. 26TH Street, New York. 



Structure andT function of the Mammary Gland.* 



By Dr. MORGAN WILLCOX AYRES, 



MONTCLAIR, N J. 



The mammalian characteristic is found in the gland whose secretion is the 

 destined food of the offspring, and which is usually found in relationship 

 with the associated generative apparatus, assuming many and varied situa- 

 tions, at one extreme being inguinal, and at the other, and highest, pectoral. 



Secretion of milk is the work of this specialized gland, and from simplic- 

 ity to complexitv of structure, a gradual differentiation is found in passing 

 from the monotremata to man ; its difference in genesis is more apparent 

 than real ; its function, always, elaboration from the mother's blood of the 

 mammary secretion. 



External appearance of position and number may mislead, yet the micro- 

 scopical structure shows one general type, from the simple cluster of isolated 

 follicles in the echidna to the elaborately formed gland of the highest mam- 

 malian. 



Following the general law of glandular development, the human mammary 

 gland is first seen about the third month of uterine life, in the form of a small 

 projection from which processes radiate, giving rise to the glandular follicle and 

 ducts. 



The position and minute anatomy of the human female gland typifies, with 

 few exceptions, the whole mammalian series. 



There is one gland upon each side of the median line, between the sternum 

 and axilla, reaching from the third to the seventh rib. 



They may be divided into internal, the proper secreting structure, con- 

 cealed under the skin, and the external, the nipple and surrounding areola; 

 the whole i-esting upon the ribs, encapsuled by a strong fibrous envelope, or 

 suspensory fascia, which sends prolongations into the gland itself, forming 

 fibrous trabeculge, dividing the organ into many compact single glands ; like- 



* See report of meeting of Essejc Co. (N. J.) Mic. Soc. Jan. 5, '88, p, 57 



