Answer: Trichinella spp. larvae
Congratulations to Chris, Sue, Anonymous, and the UVM resident who wrote in with the correct answer. This is a beautiful example of Trichinella larvae in skeletal muscle. Unlike the 2-dimensional histologic section, the squash preparation allows you to visualize the 3-dimensional nature of the larva in the muscle nurse cell. To faciliate this type of preparation, you can either press the muscle between 2 glass slides, or use a specially designed instrument - the Trichinelloscope. There is also artifical enzymatic digestion and PCR, both which can be used to identify Trichinella sp. from muscle biopsies.