88 THE AMERICAN MONTHLY [March 



This paper has another beautiful feature about it that shows to the older 

 ones as well as to the younger that there is not any subject exhausted yet. 

 Every increase in knowledge makes an old subject a new one, and this sub- 

 ject has been made alive and interesting. 



Mrs. S. P. Gage — It has l)een very pleasing to notice in this study that 

 the evolution of tissues is coming to be considered of eqnal interest with the 

 evolution of the grosser structures. 



Professor E. W. Claypole — We have the evolution of these tissues and 

 of these animals to consider. Unfortunately, from a geological standpoint) 

 we can not get tissues, 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 occurred to me that that is partly connec- 

 ted with the change that took place when land-life tirst began. As long as 

 the reptiles were confined to the sea the animals possessed the advantage of 

 breathing through their skins, but land-life deprived the animals off 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- 

 creased oxidation of blood in the lungs. 



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

 alone among the mammalia possess these oval blood corpuscles? That is a 

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

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

 blood of other creatures. The lampreys can be carried back to the Devon- 

 an era, and if they possessed blood discs almost spherical, then these must be 

 prerequisites of very ancient vertebrates. If the lamprey goes back to the 

 Devonian age, it counts among the very early ones. 



Dr. 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 

 about its variations, changes and susceptibility to not only the solids but 

 those now going undfcr 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 status. It is import- 

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



Disinfection of Mails from Plague Districts.— The Pen- 



sylvania State board sug-g-ests to the Post-master General, 

 in view of the fact that the plag-ue is a g-erm disease, the 

 importance of taking- the necessary steps to insure the 

 disinfection of all mails coming from districts in which the 

 disease may prevail. 



