464 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Similarly as to leucocytes, Ranvier found those of the frog moving 

 in a moist chamber after eight days, and Recklinghausen till the twenty- 

 tirst day. And as to red blood-corpuscles, Cornn found evidence that 

 those of the dog could survive in extracted blood kept on ice for eight 

 to ten days. 



.Many observations have been made on ciliated epithelium, since its 

 evidence of life is obvious. Engelmann found the cilia moving in the 

 tracheal epithelium of man three days after death. Grawitz observed 

 ciliation at the end of the seventh day after excision ; Busse after 

 eighteen days. Becker observed ciliary movement in cells of the epidi- 

 dymis of the ox eight days after excision. Valentin observed ciliary 

 activity for weeks after death in the toftoise. Zielonko placed pieces of 

 mucous membrane from the frog's mouth into a dorsal lymph sac, and 

 observed ciliation after five months. Schumacher has confirmed this, 

 finding that isolated epithelial cells may live for weeks, separately or 

 in multicellular masses, in the dorsal lymph sacs. 



A piece of human skin may be grafted on after being kept for 

 twenty-four to forty-eight hours in salt solution. Brewer has stated 

 the limit at thirty-six hours, but Ljunggren found that a week could 

 be reached in ascites-fluid. Thiersch found that a skin-graft was not 

 killed by the low temperature of ethyl-chloride, and Lusk succeeded 

 with a piece that seemed as dry as parchment. Oilier found a piece of 

 rabbit's periosteum living after twenty-four hours. Grawitz succeeded 

 in grafting the cornea of the hare after nine to twelve days at low 

 temperature, followed by a soaking in frog's lymph. 



The heart of the tortoise removed from the body may be made to 

 beat for hours after four days, or after a longer period if it be washed 

 internally with suitable salt solution. The heart of a boy who died of 

 inflammation of the lungs was removed by Kuliabko twenty hours after 

 death, and was washed internally with Locke's fluid. After about 

 twenty minutes weak beats were induced, which lasted for about an 

 hour. Slight pulsations of ventricles and auricles may sometimes be 

 observed in the human heart even thirty hours after death. There are 

 great individual differences. 



Roux began the remarkable experiments known as " explanation," 

 the culture of excised tissues or parts in suitable media. Leo Loeb 

 showed that epithelial tissue could grow in agar or blood-serum. The 

 methods have been greatly improved by Harrison, who cultivated pieces 

 of frog embryo in drops of lymph in a hollow slide. He succeeded in 

 keeping fragments living for four weeks or so, and observed differentia- 

 tion inprogress. Thus cells taken from the myotomes became typical 

 striped muscle, and often showed contractility. Cells from the primor- 

 diuin of the nervous system showed ainceboid movement, and the out- 

 growth of an axis-cylinder process into the coagulated lymph. The 

 process arises actively like a pseudopodium, and retains amoeboid move- 

 ment at the distal end. Burrows used blood-plasma instead of lymph, 

 and worked with embryonic tissue of frog and chick. The work of 

 Carrel and others is referred to. Carrel alternated a period of visible 

 activity in the culture-medium with a period of latent life in Ringer's 

 solution and at low temperature. In this way he kept embryonic tissue 



