172 SCIENCE PROGRESS. 



arranged an apparatus by means of which variations in the 

 volume of a limb or other organ might be easily recorded 

 whilst still in connection with the living animal. This he 

 called a plethysmograph. Very many investigations have 

 been made by it. By means of it one can show that the 

 volume of the arm, or a limb, varies with the activity of the 

 brain, and over and over again has the writer seen the 

 effect of a mental effort — -e.g., an arithmetical question while 

 being solved by the person experimented on — varying the 

 amount of blood supplied to the arm, and therefore the 

 volume of the limb. Many other Italian pupils flocked to 

 Leipzig — for Ludwig had always profound sympathy with 

 his Italian "young friends". Perhaps it will not be taken 

 amiss by his Italian confreres and friends if the writer ven- 

 tures to express his opinion that the extraordinary activity 

 in physiological circles manifested by the younger Italian 

 pyhsiologists is largely if not directly due to the inspiration 

 of Ludwig. 



As Italian pupils, we may mention Ceradini (1871), 

 perhaps one of the most talented amongst his compatriots. 

 Alas, that Ceradini should have turned his attention to other 

 affairs! His research on the semi-lunar valves is one of 

 the best monographs on this subject, and still remains a 

 classical memory. Gianuzzi, who has given his name to 

 the "crescents" which occur in the acini of certain mucous 

 salivary glands, and then followed Luciani, Mosso, Gaglio, 

 Baldi, Grandis, Fano, Martinotti, and many other well- 

 known Italian investigators. 



By a comparatively simple method Ludwig showed the 

 connection between serous cavities such as the peritoneum 

 and the lymphatics, and demonstrated how the respiratory 

 movements aid in the passage of lymph and even particulate 

 bodies from the peritoneal and pleural cavities into the lym- 

 phatics via the stomata. With his first assistant in his 

 histological department, Schweigger Seidel, who died early, 

 he invented the now familiar method of injecting lym- 

 phatics by the " Einstich " or " Puncture " method. Briicke 

 had discovered the value of soluble Berlin blue as an injec- 

 tion mass, but it remained for Ludwig, reasoning from the 



