312 



Dr. L. C. Wooldridge. 



[Apr. 28, 



animal, while in a small-toothed form the same retardation, if present- 

 by inheritance, would cause a more or less disadvantageous gap, best 

 filled by the assumption of a milk tooth. 



The first stage, or stage of retardation, appears to be still repre- 

 sented in the anterior upper incisors of many Polyprotodont Marsupials, 

 and it is therefore believed that these teeth now represent the stage 

 at which the ancestors of the Marsupials and Eutheria diverged from 

 one another, a stage at which the further development of milk incisors 

 was just commencing. 



Following out this idea, it is shown how easily the transition from 

 the Metatherian to the Eutherian stage of tooth- change may have taken 

 place, a transition by the help of which a complete series of diagrams 

 can be drawn up, following the history of each individual tooth, from 

 the dentition of the earliest Mammals, homodont and monophyodont, 

 as no doubt the unmodified Prototheria were, down to the varied 

 forms of dentition, heterodont and diphyodont, existing at the 

 present day. 



All the orders of Mammalia fall easily enough into their places in 

 the main line of this scheme with one exception, namely, the 

 Edentata, in whose case the evidence all tends to prove the correct- 

 ness of Professor Parker's suggestion as to their nearly direct 

 derivation from the Prototheria, a suggestion that the characters of 

 their teeth most fully support. On the same principles, therefore, 

 as the main Proto-meta-eatherian line of tooth development is drawn 

 up, a side branch, for which the name " Paratherian " is suggested, is 

 made for the Edentates. Within that branch very little heterodontism 

 has ever been developed, but otherwise the changes, except in the case 

 of the as yet inexplicable dentition of Orycteropus have been of the 

 same nature as those in the main line, the superaddition of a milk set 

 of teeth in Tatusia being, as in the Meta- and Eu-theria, the last and 

 most highly specialised development. 



IV. " Note. on Protection in Anthrax." By L. C. Wooldridge, 

 M.D., D.Sc., Demonstrator of Physiology, Guy's Hospital. 

 Communicated by E. Klein, M.D., F.R.S. Received April 

 16, 1887. 



Hitherto in the few cases in which protection against zymotic 

 disease has been found possible, it has been effected by the communi- 

 cation to the animal of a modified form of the disease against which 

 protection is sought. 



I have succeeded in protecting rabbits from anthrax by an alto- 

 gether different process, and although this is scarcely, at present, of 

 practical utility, it may perhaps be found to be of some interest as 



