LYMPHATIC HEARTS. 59 



animals this function is discharged by the same 

 machinery which moves the blood ; whilst in the 

 vertebrate an additional system is brought into play, 

 known under the name of the lymphatic. In fishes 

 this system is exhibited in its simplest and most 

 diffused form : these vessels being extensively dis- 

 tributed through the superficial and deep seated 

 parts of the body; they are also extremely disten- 

 sible, and have no valves, as in the higher animals. 

 In reptiles, although the general character of the 

 system is much the same, yet the following pecu- 

 liarity has recently been discovered by Professor 

 Muller, namely, that pulsating dilatations of the 

 lymphatic trunks very generally exist ; and it is to 

 these he has giv^en the name of lymphatic hearts. 

 The Berlin professor first discovered them in the 

 frog, and subsequently in toads, salamanders, and 

 lizards. In the first named animal there are two 

 pairs, one situate in the neck, subservient to the 

 upper extremities, and the other, near the hip- 

 joint, to the lower. These last are placed imme- 

 diately under the skin, and can be readily seen act- 

 ing in the living animal ; pouring their limpid con- 

 tents into some continuous vein. Their pulsations 

 are totally independent both of the heart and of the 

 respiration; they continue after the removal of the 

 former, and for an hour or two after the apparent 

 death of the animal. Neither are they synchronous 

 with each other on the two sides of the body, nor 

 always performed in the same space of time; they 

 are often irregular, and exhibit long and frequent 



