1885.] 



On the Skull in the Mammalia. 



129 



weak to be perceived on the tongue causes prolonged cardiac stand- 

 still. 



The passage of a constant current through the inter j ngular part 

 appears to cause an acceleration in the rhythm. 



B. Effects of Vagus Stimulation on the Ostial Parts of the Sinus. 



When either the right or left vagus nerve is stimulated the rhythmic 

 power of both the right and left ostial parts is completely suspended 

 for a time. The excitability to direct stimulation also is temporarily 

 annulled ; no contraction is caused by the application of even a power- 

 ful direct excitation. 



As a secondary effect of vagus stimulation there often occurs a 

 marked heightening in the rhythmic power of the ostial parts, and a 

 consequent acceleration of the rate of the heart's action. Probably 

 there is also in some instances an increase in the excitability of the 

 ostial parts. 



Weak or strong interrupted currents applied to the ostial part cause 

 an immediate arrest of the heart's action, with the usual features of 

 the inhibited state. Such a result is obviated by the administration 

 of curare. 



III. "On the Structure and Development of the Skull in the 

 Mammalia. Part III. Insectivora." By W. K. Parker, F.R.S. 

 Received January 15, 1885. 



(Abstract.) 



Although this paper is confessedly only a fraction of what is neces- 

 sary to be done in this polymorphic order, it shows at least how 

 difficult a group it is to handle. ' For the Insectivora are set in the 

 midst of the other Mammalia — low and high. They might be called 

 the Biological stepping-stones from the Metatheria to the Eutheria. 



One thing can be done, even now, with our present fragmentary 

 knowledge of the structure and development of the Insectivorous types 

 — we can assure ourselves that these types are immediately above the 

 Marsupials, that they have the Bats (Chiroptera) obliquely above 

 them, that their nearest relations must be sought for amongst extinct 

 Eocene forms, and that, lowly as they are, and arrested and often 

 dwarfed to the uttermost (so that nature could not safely go further 

 in that direction), they are rich in prophetic characters that have 

 come to perfection in larger and nobler types. 



I think it will not be denied that in the ascent of the types the 

 Chiroptera are above the Insectivora, and, as it were, a sort of special 



VOL. XXXVIII. K 



