NGC 4565 is a very large and bright galaxy. According to the Principal Galaxy Catalog, NGC 4565 is intrinsically 5.4 times brighter than the Milky Way. That's a lot. Admittedly the Principal Galaxy Catalog may be overestimating the brightness of NGC 4565 somewhat, as the this catalog puts NGC 4565 at a distance of 46 million light-years, rather than 40 million light-years, as the caption of today's APOD tells us. It is still clearly a very bright galaxy.
You can actually tell from the general appearance of NGC 4656 that it is probably a very bright galaxy.
Let's compare it with NGC 891, which was one of today's links.
As it happens, both these images were made by Bob Franke!
According to the Principal Galaxy Catalog, NGC 891 is a much smaller galaxy than NGC 4565. While NGC 4565 was estimated to be five times brighter than the Milky Way, NGC 891 was estimated to be only about as bright as our own galaxy.
If you compare the two galaxies, you can see that NGC 4565 looks "cleaner", "straighter" and more "perfect" than its edge-on "cousin". The bulge of NGC 4565 is a bit more "rounded" and "puffed up" above the disk of the galaxy than the bulge of NGC 891, and it is also brighter than the bulge of NGC 891. The dust lane of NGC 4565 also seems straighter and thinner than the dust lane of NGC 891. The dust lane of NGC 891 is coarser, thicker and more uneven, and unlike the dust lane of NGC 4565, it extends almost to the edge of the visible disk of the galaxy. Close-ups of the two galaxies will show that the dust lane of NGC 891 has prominent "dust chimneys", where huge amounts of dust are blown in tremendous plumes for thousands of light-years above and below the plane of the galaxy. NGC 4565 has dust chimneys too, but much weaker ones.
Closeups will also show that NGC 891 has prominent star formation regions in parts of its dust lane. Such obvious star formation regions are missing from the dust lane of NGC 4565.
Importantly, the disk of NGC 4565 seems larger and more wide-ranging than the disk of NGC 891.
Conclusions? NGC 4565 has a larger disk and a brighter bulge than NGC 891. Its dust lane is thinner and straighter and shows few signs of active high-mass star formation. NGC 4565 therefore has a very large population of old yellow stars, but it is relatively poor in gas, dust and bright young stars.
NGC 4565 is relatively "quiet". It is quiet in that it isn't currently forming very many stars. Since star formation is a somewhat messy affair, the general lack of star formation in NGC 4565 contributes to its "clean" and majestic shape. It is, on the other hand, obvious that NGC 4565 has been forming stars very actively in the past, which is why it has so many old yellow stars.
NGC 4565 is a remarkable galaxy that would certainly have deserved to be in Messier's catalogue. Thanks to Bob Franke for the very fine image of it!
Ann
NGC 4565: Galaxy on Edge
Good background material! 
