Bull. U. S. B. F., 1930. (Doc. 1097.) 
Figure 3. — Shells of Proptera alata, pink heelsplitter (upper), and Amblema coslata, three-ridge (lower), 
with “windows” ground in the valves to expose pericardium and heart. Through such windows 
numerous blood samples could be drawn from a single individual, as animals so prepared often lived 
for a week or more 
