This photograph is a bit strange. The first thing you need to do is get oriented. Three o'clock is a lobe of the lung. At 6 o'clock is the heart. So, at 9 o'clock we are looking at the front end of this animal. From the upper center of the photo extending toward 1 o'clock, the whitish band is aorta. That should make the identity of the organ extending from the upper center of the slide toward 7 o'clock more or less clear and with all that orientation you ought to be able to take it from there. This is an ox. I think it was a 7 or 8 month old ox which was a bit strange. It would have been much more appropriate had this been a puppy maybe 4 to 8 weeks old.
What I'm saying is that this lesion is much more common in puppies at that age than it is in cattle of any age.
