88 TUK AMERICAN MONTHLY [March 



Tliis paper has aiiollit'i l)taiitirul leatiue altout it tliat shous to the older 

 ones as well as to tlie youn<:er that there is not any subject exhausted yet. 

 Everv increase in know ledge makes an old subject a new one, and this sub- 

 ject has been made alive and interesting. 



Mrs. S. V. (iajie — It has l)een very pleasing to notice in this study that 

 the evolution of tissues is con)ing to be considered of equal interest with the 

 evolution of the gro.sser structures. 



i'rofessor E. W. Claypole — We have the evolution of these tissues and 

 of these animals to consider. Infortunatelj', from a geological stand point- 

 we can not get tis.sues, except in a few cases, to replace what these ancient 

 creatures possessed in the way of tissues. If we trust the embryologist. 

 there must have been some change going on in the course of the evolution of 

 these animals on the earth, and it nccurred to me that that is partly connec- 

 ted with the change that took place when land-life first began. As long a.s 

 the reptiles were confined to the sea the animals pos-seased the advantage of 

 bieathing through their skius, but laud-life deprived the animals of the 

 power of breathing through the skin, and that along with the Increased bur- 

 den of breathing through the lungs. The change took place .somewhere in 

 reptile life : that change was accompanied by the necessity for greatly in- 

 crea.sed oxidation of blood in the lungs. 



We then have to consider such a (juestion as this : Why should the camel 

 alone among the mammalia possess these oval blood corpu.sdes? That is a 

 iiiuestion not yet answered by the paleontologists. The lamprey may be 

 regarded as a highly specialized parasitic creature, because it sucks the 

 l)lood of other creatures. The lampreys can be carrietl back to the Devon- 

 an era, and if they jiosse-ssed blood discs almost spherical, then these must be 

 prere<iuisites of very ancient vertebrates. If the lamprey goes back to the 

 Devonian age, it counts among the very early ones. 



T)r. V. A. Moore — No tissue is more largely affected in the diseases of 

 animals than the blood, although much is known. Still little is known 

 al>out its variations, changes and susceptibility to not only the solids but 

 those now going under the name of toxin and antitoxin. This paper opens 

 up the field of the variability of structure of the blood in the same individu- 

 al regarding atmosphere and temperature, food, and so on. I do not know 

 of an exhaustive treatise on the blood of a single healthy animal, and it is 

 on the healthy condition that pathologists base their stjitns. It is import- 

 ant we should study the condition of the blood in a single specimen. 



Disinfection of Mails from PlagueDistricts. The Pen- 



svlvania Stiitc i)()ar(l sujj;-,y;csts t<> the Post-master (xcneral. 

 in view of the fact that the i)his,'-iie is a g-erm disease, the 

 importance of takin^r the necessary steps to insure the 

 disinfection of all mails coming- from districts in which the 

 disease may prevail. 



